Let me know when mpv can run on a smart TV. Most people watch via smart tv/streaming box (roku, google tv, etc), so the players work for them there.

The real competition is Plex/Emby/Jellyfin allowing access to people's media libraries in a way that's mostly on-par with existing services, and the added benefit of having all content truly in one place. The issue is that there isn't a completely legal way to get media content as unencrypted files (since ripping blu-rays is legal, but breaking the software protections to do it isn't).