Income generated from printed music royalties are pretty small these days, but they do still exist! These were the first publishing royalties known to the world and why the term "publishing" was used to describe this part of the music industry.
Long before anyone had CD players or radios, people bought sheet music to play on an instrument at home, parlor room, or concert hall. Like a book publisher, music publishers made this sheet music available for purchase. Hence, these royalties are generated whenever sheet music is purchased and only go to songwriters and publisher.