Android's Problem is fragmentation, and it wouldn't help at all to just backport some functions to older devices, because then developers coulnd't be sure about tthe availability of any API.
By contrast, my Galaxy Nexus has become slower and slower with each upgrade. With the last update, my keyboard started to crash... I was really looking forward to the 4.4, hoping things would improve.
And yes, I use two phones and most of the time have both with me... GN is no longer used as a camera though.
You get this on the 4S, yes, just not on the iPhone 4 or the iPad 2/3.
> because then developers coulnd't be sure about tthe availability of any API.
iOS 7 running on the iPhone 4 has the same APIs as on the 5S; it just doesn't have all the UI features (notably, the blurring stuff).
Contrast that with Android, where developers are still targeting Gingerbread and are unable to take advantage of any of the bug fixes in ICS, JB or KK.