Lots of stuff does not get reprinted. I read romance and a lot of the books are designed to be ephemeral and just to be on the shelves for a short period of time before being replaced with new books.

Also the cost factor. Getting to pick up 10 books for what one new paperback would cost.

On a separate but related note, I need more bookshelves....

There isn't anything I would rule out completely, personally. It all depends on how the writer approaches it and how they deal with the material.