The other large factor is copyright. If we had 21 year copyright terms for shows and movies, I'd imagine someone would have set up a streaming service with every show and movie under the sun that they could fit into that, and people would eat it up, since they often just want to half-watch Seinfield, Friends, Star Trek, et cetera, since its their comfort show. A service that can provide that without being hostile is quite a lot of what many people look for in a streaming service.