Ironically, Microsoft's compatibility commitment has boomeranged, making it easy for users to keep what they have Microsoft’s 13-year-old Windows XP won’t go away, as much as Microsoft tries to cajole and threaten users to abandon XP. In fact, it’s the second-most-used version of Windows today (at 34 percent of users), though three versions of Windows shipped after it. Contrast that to OS X; its oldest version in widespread use (Snow Leopard, at 19 percent of users) is not even five years old, and the version released last fall (Mavericks) already has 48 percent of the Mac user base. By comparison, Windows 8 is at only about 4 percent of the Windows user base.Let me fill you in on a secret: The reason that people avoid upgrading Windows but not OS X has nothing to do with one platform being better or worse than the other, Windows 8 notwithstanding. It’s about a fundamental decision both companies made nearly 30 years ago that has largely served them well but has aliso led to the upgrade split they have today.[ Want a new PC but not Windows 8? Our picks for the best 12 Windows 7 PCs still available. | Subscribe to InfoWorld’s Consumerization of IT newsletter today. ] Today, as Microsoft’s April cutoff for Windows XP support nears, people are begging for yet another extension, and Microsoft is reeling from the loud demand. Its customers seem determined to run XP forever, thwarting Microsoft’s desire to modernize the PC. Although nearly a fifth of Apple users cling to Snow Leopard (mostly on old systems that can’t run a newer OS X version), the Mac user base by and large moves forward with Apple.You can see the breakdown in the chart above: As of December 2013, two months after its release, nearly half of Mac users were running OS X 10.9 Mavericks, while as of February 2014, 16 months after its release, only 9 percent of Windows users were running Windows 8.x.To be clear, the Net Applications data here is biased in favor of Internet-attached PCs in Western countries. It’s estimated there are at least as many PCs running pirated copies of XP in countries like China and India than there are in the West. The actual XP percentage is likely twice what’s shown here, with the other Windows versions reduced proportionally. There’s also a sizable but unknown number of non-Internet connected PCs used as instrumentation systems and the like that Net Applications also doesn’t count, most of which are believed to be running XP — further increasing XP’s actual percentage. Regardless of the true XP numbers, the pattern is quite clear. What is it that causes Windows users to cling to ancient versions of Windows?The key decision Microsoft made for Windows: Universal adoption You can point to several reasons, some tied to Microsoft’s past strategy and now acting as a ball and chain. In addition, some users simply don’t like what Microsoft is doing to Windows, and they see no reason to suffer the madness that is Windows 8. That’s not the primary factor, but it exacerbates the main mover.That primary reason is Microsoft’s decision very early on to make Windows a universal operating system, with a PC on every desk, as founder Bill Gates exhorted his employees to achieve. That meant Windows had to support anything and everything. Compatibility for software and hardware was a critical aspect of the Windows plan, and Microsoft has undertaken Herculean efforts to make sure that practically anything that ran under Windows 95 still can run today, nearly 20 years later. It also gave customers, hardware makers, and developers lengthy lead time to align to Windows changes with minimal disruption. By contrast, Apple decided early on that its Mac platform would evolve regularly, and it would cut off old software and hardware ruthlessly to ensure a more homogeneous environment. Customers and developers were often marooned with no notice, though Apple has improved in providing a grace period in recent years. Apple customers know they’ll get about five years of compatibility when they buy a Mac; after that, they can expect new OS X versions, hardware drivers, and services to not run on their old Mac. In fact, that incompatibility accounts for most of the OS X 10.6 Snow Leopard-based Macs still in use — they’re running Macs that cannot run 10.7 Lion or later. So as far as Apple is concerned, they now need to get a new Mac or assume the risk of being an orphan.Apple’s strategy meant that only a tiny proportion of the world’s apps run on OS X, as do very few specialized hardware devices. The percentage of Macs in use has also been tiny, ranging from 3 percent of personal computers in use at Apple’s nadir in 1999 to about 7 percent today — which is less than the total Windows 8 user base. By many measures, OS X is a failed platform for a sliver of humanity willing to keep buying new Macs for essentially emotional reasons.Microsoft’s strategy created a global standard that runs practically every business and home, for everything from gaming to weather modeling. Your kids use it to do homework, you use it to manage your budgets at work and write memos, banks use it to run their ATMs, and NASA used it on the space shuttle. Few products have been as universally and deeply adopted. We tend to forget that when we see the ongoing decline of the PC and the rise of mobile devices, or when we see Mac sales continue to increase (or, more recently, stay even) as Windows PC sales decline, or Apple scoop up nearly half the profits of the PC industry despite its tiny sales percentage. Those are all recent phenomena that have more to do with the end of one PC era and the start of a new one. And they don’t explain why Windows users stay with older versions far longer than OS X users do.Microsoft’s perverse compatibility strategy: Technology wins, users lose You’d think that Windows users would happily keep up with the latest Windows versions, like Mac users do with OS X. One reason OS X users upgrade more, beyond having bought into Apple’s “you get five years” implicit mandate, is that each version builds from the previous one. You don’t have to relearn how to use OS X, even if you have to learn how to use new features. But you have to accept some apps or devices will no longer function — which should be a barrier to upgrading.Windows users face the opposite calculation: They can be darned sure their apps and hardware will still work, perhaps after a driver upgrade. But they typically have to relearn basic Windows functions. (Microsoft imposes the same trade-off for Office: Your files are compatible, but your UI is not.) What you get are inchworm upgrades: Users avoided the buggy Windows Millennium, Windows XP (until its early compatibility issues were worked out), the confusing Vista, and the confounding Windows 8. But they leapt into Windows 95, Windows 98, XP Service Pack 1, and Windows 7. You can’t say Windows users are averse to change — just (rationally) to bad change. Because Microsoft can’t tell the difference between good change and bad change, it forces its users to make that decision, and they’ve learned to do so cautiously and slowly, often by buying a new PC a year or two later.Internet Explorer plus hacked-together apps and device drivers held back Windows But there’s much more to Microsoft’s compatibility strategy that gets in the way of fast user upgrade adoption than favoring technical compatibility over user compatibility. This one is not entirely Microsoft’s fault.A common complaint in IT organizations is the use of apps that require a certain version of ActiveX or Internet Explorer to function. Microsoft does orphan IE to specific Windows versions, so if you need a certain version of IE to run a key custom or niche application, you literally cannot upgrade Windows. Many small and in-house developers wrote quick-and-dirty code for the then-current IE versions for such niche software, and they went out of business or decided that they or their customers wouldn’t pay for the development to get new versions. Java developers have done the same, of course, so you also hear IT complain that they can’t run certain apps because they use an old Java runtime. Microsoft’s attempt in the early 2000s to fork Java didn’t help. It’s clear that IT organizations didn’t value cross-generational compatibility in their own work or from their suppliers, so they dug themselves a hole that has now swallowed Windows.Remember: Microsoft’s deal with IT has been compatibility, which has led Microsoft shops to stick with old Windows versions to avoid the costs of upgrading their apps and even some hardware devices to work with the newer Windows. Microsoft has accommodated that by letting enterprises run older versions of Windows when they get new licenses, such as when buying new PCs. Of course, to fulfill its compatibility promise, Microsoft had to make that allowance.As a result, we now have a compatibility bramble that keeps big segments of the Windows user base stuck on specific Windows versions. Microsoft has no compatibility solution — each version of IE is essentially a new product, with no guaranteed backward compatibility, and hacks like Windows 7’s XP mode and IE’s compatibility mode don’t work well or easily. Essentially, Microsoft has been unable to keep its compatibility promise in its software, creating this mess. Sloppy development practices by IT organizations and software vendors made situation worse. Yet the customer expectation of compatibility has only grown, ironically enough.Microsoft’s clean break didn’t work Although it may not seem that way sometimes from the outside, Microsoft has a lot of smart people working for it. The folks in Redmond know that Windows has become an unmanageable mess in need of a fresh start.Windows 8 was supposed to be the transition to that fresh start: a mix of the old compatible Windows with a new Windows (aka Metro) that started clean. Apple had made its clean break with iOS, which had no compatibility with OS X, despite a common base. Microsoft, given its 30-year-old compatibility commitment, took the “two in one” transitional approach instead, which we now know is a big flop. Windows users really want that compatibility — which is why they are sticking with Windows 7 as their mainstay, and with Windows XP if they have apps or hardware that require it and only it. I suspect if Windows 8 had been a great OS with great apps, the consumer segment would have switched quickly, as Apple’s Mac users did when OS X was released in 2001. The enterprise likely would have split into “new” desktops for everyday workers and “old” desktops for more specialized use cases. Coulda woulda shoulda — it didn’t happen.Maybe Windows 9 will be what Windows 8 should have been, or maybe it won’t matter — consumers will move to Android and iOS, while enterprises move to Windows 7 and stick with it for another decade or two. Who says you need the same OS at home as you have at work?Why Apple may face its own compatibility dilemma in iOS Apple fans might be temped to gloat over Windows’ fate, but that would be unwise. There are signs that iOS is following part of Windows’ path. With iOS, Apple has created a platform that runs many more apps than ever ran on OS X. Many of those apps are specialty apps for instrumentation, music creation, and sales terminals. That should remind you of Windows’ deep history of niche uses. Many such apps make iPhones, iPod Touches, and iPads essentially into appliances. And businesses don’t replace those as often as individuals might upgrade a phone. That puts Apple under a compatibility burden it’s not used to. You can see the conservatism already creeping into Apple’s iOS product line. Until today, Apple sold 2011’s iPad 2 as a new product, and Apple kept selling 2010’s iPhone 4 until late 2013. And it still sells 2011’s iPhone 4S. What these devices have in common is that they use the Dock connector found on many specialized apps and add-on devices: radios, cars, payment terminals, music-editing controllers, medical sensors, and so on. It’ll be a long time before those fleets of devices are replaced with Lightning connector-compatible models.Althoug Apple has now stopped selling most of those legacy models, they’re examples of the new compatibility context Apple has in iOS that it did not have in in OS X. Perhaps Apple will learn from Microsoft’s compatibility dilemma and manage it better. We’ll see.In the meantime, when you see Microsoft and its partners desperately try to get you to dump XP or even Windows 7, you can sympathize with the dilemma such a switch imposes on both you and Microsoft. For many, there’s no easy way off the older Windows versions and little reason to adopt the new one. What you can do is upgrade to Windows 7 — that is, if compatibility requirements allow it. If you’re truly stuck on XP, be prepared to do what Apple is advising OS X Snow Leopard users: Take care of yourself. Microsoft legitimately can’t do so any longer. It needs to move on, even if you can’t.This article, “Double standard: Why Apple can force upgrades but Microsoft can’t,” was originally published at InfoWorld.com. Read more of Galen Gruman’s Smart User blog. For the latest business technology news, follow InfoWorld.com on Twitter. Software DevelopmentTechnology IndustrySmall and Medium Business