Wouldn't the Taylor Swifts of the world get more money at the same rate, due to being streamed more?
The unknown upstart's stuff is not being searched for and played. Is that not already the lower rate that they accept? Does the revenue also have to be lower from those few plays they got?
Theoretically, it does not have to be.
Practically, the big names are not going to accept less than the maximum they can get. Just like almost all people would if they were negotiating multiple equivalent job offers.