What you can't do in an app in the Play store is implement your own app store and load arbitrary apps. And Amazon forces you to install the full Amazon app including its app store, rather than offering a standalone version of Amazon Video.
Amazon likely does this because people care enough about Amazon Video to jump through hoops to get it, and once people have jumped through those hoops, Amazon can then try to get them to use the Amazon app store instead of Play.
I'd not be surprised if someone has built something marketable on this stack already.
[1] https://developer.android.com/training/enterprise/work-polic...
It makes sense, of course, considering that this approach will let Google -- but no one else -- know who all those identities point back to.
That's a brilliant idea, especially now that the multi-user support works on phones in addition to tablets.
http://repo.xposed.info/module/biz.bokhorst.xprivacy
This allows you discretion for apps you still wish to install but demand too many privileges.