Uncorrected Proofs in comics libraries? Keep or toss?

This question came up in the librarian section of the Comics Studies Society.

I argued in favor of keeping them as the art is frequently in an unfinished state, and can be thumbnails, pencils, or uncolored.

Here is an example of a proof, or Advance Reader Copy, of Trashed by Derf with an added editor's note and marketing information that may not be available anywhere else. It's from my own collection that I happen to run across recently, so I decided to take a few pictures to bolster my argument, and then thought I'd share them here as well.

I'd call this part of the Secret History of Comics.

My apologies for the so-so photos.