"You wouldn't stream a car for free would you?"
This is just playing with meanings but for most musicians having their music on Spotify or on torrents is pretty much the same. the only difference is that only in one case there's a company profiting in the process.
Musicians put their music on Spotify out of their own will. If they don't like it they can withdraw. Unless they sold the rights to a music label, but that's also their decision.
