Because Android is a touch-centric OS. I've picked up some HDMI sticks that put a decent skin on Android and use an AirMouse for the UI, and it's not fun. Most of the apps use drag-based scrolling which is painful with an airmouse, and on-screen keyboards.
That said, a simple clean airmouse is so much nicer than the zillion-button monstrosities of traditional TV remotes.
