Then they will fail.
People want one box that does it all. Not a GoogleBox, AppleBox, and an AmazonBox. That's madness.
They want one box, preferrable for less than 100 bucks, that will play Hulu, Netflix, Prime, Vudu, Youtube, GooglePlay, iTunes, Plex, etc.
Right now, the _only_ way to do this with one box is to build your own NUC HTPC for a couple hundred dollars.
Amazon offers Amazon devices because they think you will be a better customer if they control the complete experience. However I can't imagine they would stop supporting Prime Video and Kindle on Android and iPad just to pump up their own device market. That's putting the cart before the horse.