Singers are rich, in contrast musicians are poor, most of them are poor.
It is not fair, in my opinion.
And, free music tracks are abundant on online sites, and other places are one of components contribute to make musicians are poor. I dont like it, to be honestly.
What makes you believe that singers are rich? That's also seldomly the case, or do you mean in a band the singer is richer than his band for example?