1) The site is setup for individual musicians, not bands or acts. I'm really targeting the high school kid who sits on his bed and plays lightening-fast guitar solos. He doesn't have anything to sell.
2) If I promised that kid he'd make significant (to him) $$ selling his music, I'd probably be lying.
3) Most musicians aren't going to make money selling their music. But they get a high out of having lots of people listen to it. So I'd rather just let people give it away for free and optimize for generating lots of plays, which would make them happy. Vs helping them sell it only to be disappointed.