Wasn’t only blues artists. The Small Faces were royally screwed over by Sharon Osborne’s dad. The Honeycombs didn’t get anything for years from Have I The Right. Bert Berns, who wrote and produced some great stuff https://en.wikipedia.org/wiki/Bert_Berns (put a link as there are too many to list) did Van Morrison over when recording Astral Weeks and Moondance which ended up with him not getting a penny for Brown Eyed Girl, a song which at one time had more radio plays in the USA than any other and will still be in the top few.
