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?
People don’t like to hustle with pirate sites if given reasonable alternatives. Currently youtube, spotify, apple music and online radio stations fulfill these demands. Just like netflix originally killed most of pirate streaming, it was easier just to pay a bit to get all the content, then content providers decided each to create their one limited content service and pirates were back in business. Once you’ll have to pay a different providers to hear different songs you’ll start seeing more and more pirate music streaming sites.