AOSP is way too fragmented. An "app" dating back to, e.g. Android 2.3 (not that long ago), or even as late as Android 4.0 will not even build in a form suitabl

AOSP is way too fragmented. An "app" dating back to, e.g. Android 2.3 (not that long ago), or even as late as Android 4.0 will not even build in a form suitable for a present-day version of AOSP - you have to go and rewrite the code yourself, there is no backward compatibility that reaches that far. Linux platforms are truly mature and can easily run code dating back to the 1980s. Add to that the pointless overhead caused by Dalvik/ART (especially wrt. RAM use - quite critical on a system with no swap space whatsoever!), and the gratuitous differences with widespread Linux kernel and userspace standards. Starting from scratch on a better base is short-term pain for long-term gain.