Here's a data point: I am demanding it. I purchased software and I'd like it to continue to work.

The Ace Attorney collection was excellently packaged for iOS, and I want to keep playing one of the best-published versions of this trilogy, but now the UI doesn't render properly.

I'm not saying that it's trivial, but we both know it is absolutely possible. Apple keeps putting the focus on "gaming" in its iPhone keynotes, but if they were serious about gaming, they'd make the games I already bought continue to work.

It's not an OS feature because Apple has an aversion to maintaining any kind of compatibility layer for more than a few years, it's not a third party app because Apple doesn't allow JIT code (eg. high performance emulators) in third party applications on iOS.

Demand isn't the only reason to make a feature, sometimes customers might want something only after they're given the opportunity to recognize it's value.

Designing an app to emulate iOS games would be extemely difficult, let alone allowed on the app store. Backwards compatibility requires deep forethought and careful engineering as well as draconian enforcement. I think the technical difficulty plays a huge role here, when weighed against Apple's culture (sleek, minimalist) and the impact it would have on profit.

Emulators aren't allowed on the App Store, so it couldn't be a third-party app.