I would presume that the extra steps incrementally diminish the possibility of the book remaining unsold, and thus destroyed or sent elsewhere.

And it also adds costs in every step. Someone needs to move thousands of unwanted books from high end stores to lower and lower end stores. Someone needs to store them in the proper environment etc.

I do get the _idea_ of preserving books, but... people don't care. I just threw out well over a thousand books from my grandparents house this spring.

There were ~6-10 "valuable" books there. Two because I personally knew someone who wanted old war-time books and a few 100+ year old bibles. And maybe two dozen books worth saving, mostly because they were from big-name authors or had stuff that nobody would print anymore (I have detailed instructions how to make laughing gas and how to build an underground chemical lab - hobby books in the 50s were ... interesting :D )

I literally couldn't give away the rest. And I tried. It was all just "interesting, but..." - no way to justify using the shelf space for books that, realistically, nobody will actually ever read again.