https://en.wikipedia.org/wiki/First-sale_doctrine

> After the initial transfer of ownership of a legal copy of a copyrighted work, the first-sale doctrine eliminates the copyright holder's right to control ownership of that specific copy.

How does the first sale doctrine require these horrific companies to destroy the books?

As near as I can tell, there is no legal pressure for them to do that. They're destroying them because that's how their scanning machinery works.