At least in the US, the mafiAA have a stranglehold on streaming music stations, considering them radio stations and requiring royalties payments to the industry giants (ASCAP, BMI, etc). In the early days of streaming, nobody cared.. you could have a station which had your favorite music and stream it to all your friends. Now they want you to pay to be able to do that since they consider it (which it kinda is) just another form of broadcasting.
So for probably 90% of the music out there, streaming it is illegal.