Largely, because books are heavy, and there's limited demand for most used books. If you've ever been at a book sale on the last day, there are always lots of leftover ones that no one wants.
There's a general sense that librarians are preservationists. This is far from the truth. Most books get pulped within a few years of printing. Librarians are constantly discarding books that don't get checked out to make space for new books.
There's a general sense that librarians are preservationists. This is far from the truth. Most books get pulped within a few years of printing. Librarians are constantly discarding books that don't get checked out to make space for new books.