This is rooted in the early days of cinema, in which theaters were also owned by the studios, and so would only show the stuff the studio produced. Was gonna go into it in my comment, but decided against it to keep it short. Another commenter also mentioned it, and that's pretty much what I'm proposing. I'm suggesting specifically that they have to show everything in order to also avoid exclusivity deals. Part of that, though, would also be to just not let Netflix produce its own content, but if it didn't, you'd be able to watch it on amazon anyway