It's precisely because of Amazon, you can't even buy an ATV4 on Amazon because Amazon banned the sale of them along with Google Chromecast.You're acting like there's Amazon Video even on the older Apple TV. There wasn't. There never have been. I don't expect to see on on tvOS either, ever. And that's not because of Amazon. You're argument is invalid.
http://variety.com/2015/digital/news/amazon-chromecast-apple-tv-ban-1201630010/
If Amazon wanted an app on ATV then they would of made one, but instead they'd rather you go buy their own streaming device instead.