Same as punishment for crime. Putting you in jail wont undo the crime but if we just let you go unpunished since "what's done is done" then that sends the signal to others that this behaviour doesn't come with consequences.
There's no point in torturing you but convincing you that this will happen unless you act in a certain way is what's going to make you do exactly that. Unless ofcourse you want to take your chances and call the bluff.