iOS 6 won’t be offered on devices that it easily could run on. Both the original iPad and iPod touch third-generation are faster than devices that will receive iOS 6. We only have Android to thank for it.

First, the technicals

Apple will be issuing iOS 6 for the iPhone 3GS. Apple’s aging free-with-contract affair is quite long in the teeth at this point. It defines the minimum system requirements for iOS 6. A lot of iOS 5 and iOS 6 features won’t even operate on iPhone 3GS.

You might argue that the third-generation iPod touch is somehow slower or underpowered in some key way compared to iPhone 3GS, except that you would be wrong. Every benchmark and teardown shows that iPod touch third-generation has exactly the same guts as iPhone 3GS. And, since iPod touch isn’t communicating with a cellular network, more times than not it has noticeable performance benefits over iPhone 3GS.

iPad is even that much more dramatically faster with its speedy Apple A4 chip, a chip that outperforms the same A4 used in the iPhone 4 series. Granted, some features that would run on iPhone may be compromised due to the higher-resolution display in the original iPad, but if Apple is willing to cut features easily from iPhone 3GS, why not do so and keep original iPad owners happy?

Now, the reason

The reason is that they don’t have to. Competition is what drives the slightest motivation to go back and issue updates for devices you aren’t selling anymore. Competition is why a Mac mini from four years ago can keep running the latest and greatest versions of OS X. Competition is what keeps new iPhones shipping.

And, the competition has done a terrible job of updating their devices.

Outside of Apple, Handset manufacturers blame the OS vendors for making it too difficult. Carriers blame handset manufacturers for wanting updates to be paid for. OS vendors blame the ecosystem. And, all of them want you to buy a new device anyways.

On Android, Google faces a lowest-common-denominator situation. They have tried to head that off with Android 4.0’s dramatically higher system requirements, and skipping Android 3.0 for smartphones. The result has been that most Honeycomb-era tablets have (or will) hit Android 4.0, and Android 2.3 users should make it through their contract with an ecosystem that Google has committed to seeing through for at least that long. Android 2.3, unlike iOS, is continuing to receive security updates after being discontinued.

The argument from the Apple camp, of course, is that Apple’s walled garden protects users long after they drop OS upgrades. And, as we saw with Flashback, Apple is willing to go back and issue upgrades for long-discontinued operating systems… but only after the backlash of negative public relations. It remains to be seen if the lessons learned from Flashback will result in more proactive security updates for iOS devices left in the dust.

Windows Phone has its set of struggles. Windows Phone 6.5 devices that could run Windows Phone 7 got left behind due to rigidness from Microsoft. Microsoft learned from that experience, and made sure every Windows Phone 7 device made it to Windows Phone 7.5. But the writing is on the wall for Windows Phone 7.7, and it looks like many devices that could run it, won’t get it.

Unlike Android 4.0, which few devices actually could be upgraded to, Microsoft will have to make the jump to Windows 8 Phone so massive, that no few existing device could be upgraded. Unlike Android 4.0 however, that is out of necessity; to run the Windows 8 kernel properly will require smartphone hardware beyond what is on the market today.

And if that sounds familiar, the folks up north had to say the same thing about BlackBerry 10. And, actually, RIM probably did the best job of the bunch with backporting BlackBerry OS versions, up until they had to start chasing iPhone and Android. The incremental pace of BlackBerry devices made it easy to backport OS versions. Of course, many times it was difficult to call those generations “upgrades” at all, because so few new features were added.

Conclusions? Don’t shoot the messenger.

It’s unlikely this situation will improve any time soon. Windows 8 Phone will have the benefit of bringing us closer to the PC/x86 world of having a device that truly runs like a personal computer. But, not much. Windows 8 Phone will be its own, modularized branch of Windows 8 for PCs.

RIM will probably shake things up, pitching to corporate customers much longer lifecycles than what Apple offers.

Android and iOS… don’t expect much in terms of change from today’s situation. With almost a million Android devices being activated daily, and Apple keeping pace there too, neither is likely to commit to ensuring devices get all the updates that they’re capable of handling.