Surely the people granted a legal monopoly to print the books will have kept a copy of the masters in order to reprint any lost works. Surely copyright works as intended for the public good and isn't just rent seeking. Surely.
OR in-print modern books that they can get for cheaper by buying used. The whole thing is a manufactured outrage over something that doesn't matter. They aren't breaking into museums to steal their only copy of a book and burn it. They are digitizing books. If anything I commend them for what they are doing. If the alternatives were that book rotting on a shelf or being thrown away they doing a great service preserving it, even if they don't make it available publically (which they can't for copyright reasons). It's literally no different from them stocking a private library with these books, except it's better because digital copies are much easier to preserve.