Idk. I think it’s just easier to rely on a specific someone whose job it is to put shit in the proper place than to hope every random person who takes a book off the shelf can put it back in the proper place. Like, I get what you’re saying. It isn’t a big ask to have people return a book after looking at it. But it’s so easy for them to put it in the wrong spot. And once it’s on the shelf, it’s much harder to notice that it’s out of place. It seems counter intuitive, but it’s more efficient to simply leave the book out after looking at it