They don’t have to force them to make an app. Instead they could make them provide an interface that an app can use. Instead of their current strategy of thwarting any attempt to make their ecosystem interoperable with competitor’s devices. I imagine them instantly killing Beeper’s connection to iMessage was a part of this move.
The best explanation I’ve seen is that music is mixed differently for CD/streaming and vinyl.
For mass market, the move has been to mix for louder bass and similar things. The idea being that it makes the music more popular. But it also makes it difficult to appreciate anything but the bass.
On vinyl, you can’t max out bass like that, it won’t work on the format. So they have to give it a normal mix instead, making it sound better. In theory CDs should sound better than vinyl, but because of the music production trends, it doesn’t currently.