What Is The "Reason For Deletion" Option For?

[Woodsprite]

"Reason for editing" makes sense; tell people why you've edited you message. But "reason for deletion" obviously means that the message hasn't really been deleted, but rather hidden from public view. So my question is, why does there need to be an option like this for deleting a message if the only people who can read it are moderators/administrators?

Been wondering this for a while. I've seen it in all sorts of forums, but never really thought to ask about it.