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?
Pandora? Spotify? There was another one like Pandora I used to use in high school but I can’t even remember the name of it now it was so long ago… Before all that we had shoutcasts on Winamp (basically podcasts and streaming radio). Free streaming music is older than free streaming videos, so far as my experience knows.
Not to mention radio. The original over the air “streaming” service.