The library staff is a lot more nervous about the library being empty than they are about it being full.
This I can attest to.
At our local public library there's a lady who is constantly picking up and re-shelving kids books only to have some kids take a bunch out and toss most of them on the table or the floor.
When I asked her if she wasn't frustrated, she said counter-intuitively that she's actually happy to come in to the section and find a ton of books to re-shelve.