Several movie and TV sites have come and go where you can just visit and watch without even creating an account. Quality might not be as good as a paid service and they are no doubt in the grey-to-red zone legally. I don’t see the same service for music.
Why do you think is there such a difference in trends?
Spotify will force you to listen to an ad by pausing it if you mute the volume, then resuming it when you unmute.
I quit Spotify long ago so I don’t know if they still do it today, but they do have a way to force ads.