Does that even matter? Since the marginal effort on the part of the performer is exactly zero? (which is to say they don't have to "do" anything to be on Pandora, they just collect checks from BMI/ASCAP). If a musician is arguing that they are being driven into poverty by poor royalties, losing them completely seems to make them worse off.
I would argue eliminating the streaming services would more likely make the pie smaller. I don't think all the people paying x a month or ads supported are going to suddenly start buying albums.