Why the heck after you edit your post ( after few minutes or so) it has to show that you have edited it in bottom of your post?

And why it doesn't show the edit-thingy in Admins/Knights posts? I don't care either way; I'm just curious is there any rational reasons for this. Everyone who wants, can always add "EDIT" in their posts. And for example in Aiyon when you edit your post, there's checkable option: "Add last edited line in your post", or something like that.

*Feedbacks just for the sake of his non-feedbackness*