Time was singing a song was also considered “free publicity” (or unchargeable).
The money was in PUBLISHING sheet music. You could sing a song from the stage (e.g. vaudeville) or on a record without paying the songwriter.
The songwriters would even hire song pluggers to get them INTO musical acts and pay shills to sing along to the songs from the audience so rubes would want to buy that song and be able to sing it too (50 cents a song).
This understanding of copyright law was changed too as recording took hold. Now even kids around a campfire have to pay songwriter royalties.
Yes, now it's getting stupid as the copyright cartel tries to erase the concept of fair use and lock down our entire culture for their profit.