Hit the nail on the head.

Millions and millions of print books are destroyed all the time, and very rarely is anything of value lost. Libraries, thrift stores, and used book stores get inundated thousands of books donated to them, most of which nobody wants. Unless you, personally, are going to take on sorting, transporting, and storing dozens of duplicate copies of books in poor condition, and have some purpose for them (presumably?), then get off your high horse about the destruction of bulk-purchased used books.

Individual copies of mass-published books are not precious. Only rare books are important for preservation. And, even then, digital copies are much more practical for long-term storage than physical books. Anna's Archive's preservation project as a shadow library is only possible because data storage is very cheap, infinitely replicable, and practically free to transport.