Perhaps they would have been better served by spending their time getting HBO-Go, Starz/Encore and Spotify all hooked into their little box
Give it time. These are usually 3rd party apps not built by the provider of the platform (as a note, my company just finished building Starz/Encore/Movieplex Play for Xbox 360). The important thing is that Amazon provides an Ecosystem,it just needs some time for all the other offerings to get on there.
The SDK just opened up to all third parties today as well https://developer.amazon.com/public/community/post/Tx1K5ORNN...