I even read on a web site of a librarian that their library had stopped accepting donations because "patrons should know how to throw away their own trash".
What happens when the books don't sell?
Many books aren't lent and not bought and most libraries have limited space to store such books, thus they go where old paper goes.
Of course some rarely lent books are important and for the one person asking for it in ten years really valuable, but many still have to go.
I know it comes at a shock but truly most books are absolutely worthless.