Ad backed music streaming has become an unexpected major source of income from music labels. That's also true for indies. I don't make money off youtube directly however my distributor claims videos using my music and I make money off ads on youtube indirectly. The payout isn't big, but it's not insignificant either.

I imagine a lot of major artists make good money off youtube too. They don't if someone just downloads their videos. In times where musicians can't make money off concert, it's even more meaningful. Google does work directly with all these music labels (VEVO and co...).