> You could have the worst software and the best content and probably win
I definitely get where you're coming from. As a counter example, my parents aren't great with tech and have written off platforms with content they want because they find them annoying. For example, they find Amazon Video way too confusing. What's free? Why are there channels that aren't free that they already have somewhere else?
> I suppose the answer is to let the users write their own clients
Netflix definitely doesn't want this. They want people to turn on their TV and open Netflix. If people have a third-party client that can show Netflix content alongside content from HBO, Amazon, Apple, and Disney, people might start watching their competitors more.
Not only that, but Netflix wants to be able to push your viewing in certain ways. If everyone starts watching a show at the same time, it can create buzz. Netflix's big promotion of Squid Game got to that critical mass for buzz to happen.
If they're able to determine what comes up where in the UI, they can also prioritize shows that are cheap for them. Getting someone interested in an owned show is better than getting someone interested in a show that they're renting from a third party.
That said, there are third party UIs like JustWatch that allow you to integrate with multiple services. We also saw Movie of the Night (https://news.ycombinator.com/item?id=29862588) featured here a little while back offering an API and it does offer links to shows in Netflix.
I think the issue is that it takes work to build a third-party UI and it takes money to actually collect the data (or pay someone else for the data) while the streaming companies aren't totally happy about giving you that data.
Really, everyone is looking for an edge. Google wants their Android TV to serve you ads for shows. They want Hulu to pay them money for them to push Hulu shows in their UI even if you don't have Hulu. Roku wants to sell advertising space on their Home Screen. Every content provider would love to become your primary destination while you ignore the other apps on your system and forget that they have content too.