Earlier quoted context omitted.
The library can buy the stuff used and the publishers make nothing off of such sales. I buy nearly all my books used.
Libraries cannot buy used because they need the asset prepared for circulation. This includes a protective cover, barcoding, etc. They usually have a vendor do this preparation, and the assets (books, usually) are often not the same as what you would find in a store, they can be different sizes to fit in Automatic Materials Handling Systems, have more robust binding, etc.
It's possible to put a protective cover on a used book.
The books at my local library come in many different sizes, including the size of a paperback novel.