Stores were stuck with a glut of “high priced” but worthless shiny books that no one was reading (”these are for resale later!”).
Back in the olden days an unsold book had it’s cover torn off and sent back to the company. The book was then destroyed.
If you knew where to look, you could find stores with lots of books with mutilated covers, and torn off titles on comic books for a few cents. They weren’t destroyed.
You can still get magazines that way too.
Some will toss them by the entrance/exit door.
The big brick and mortars don’t send back the full unsold paperbooks or magazines that they stock. They rip off enough of the cover to get reimbursed and save on postage.