While i understand that the patches needed to "support" Android operations aren't in the mainline kernel distribution, I don't understand why it isn't being ported to newer kernels.
Newer kernels come with a load of improvements in a lot of architecture-independent areas, as well as in a lot of architecture-dependent areas.
FWIK, I see almost all Android distros, starting with Google's, are sticking with kernel v3.4. Yes, v3.4.112 is an LTS kernel, but so are v3.10, v3.12, v3.14, v3.18, v4.1 and v4.4! (source: kernel.org).
So, what is holding Android back to v3.4?