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?
It’s because streaming in movies is exactly the same one thing everyone thinks about, while streaming in music is dozen of different things and you meant just a single particular one while excluding all others. If we consider all types of music streaming, there are countless free streaming services for this: youtube, soundcloud, mixcloud, spotify, thousands of internet radios.