Well, plexamp is a dealbreaker for Apple that more and more wants you to buy Apple Music and all their services. They have more to lose by opening to plexamp users, who are not the more prone to spend money, or other services, than to lock users in their very own walled garden. Open source software on consumer friendly hardware is the way now.

I don't know if that's obviously true. I'm sure Plexamp is small potatoes compared to how many are on Apple Music, and there's a solid chance that anyone running a Plex server is doing it on a Mac.