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?
Availability. You can just straight up search on YouTube to find a song and find it. Same goes on Spotify. If you’re not an audiophile, no one would care if the song quality is low. If you listen to well known songs, you can likely find the music files available on public trackers and youtube.
If you care about a certain style of music not available on public tracker and want higher quality files; you likely can find a private tracker invite through people that listen to it. So there’s no reason for both people to use a music piracy site.