If someone wants to steal your work, a little red or green flag on your profile isn't going to stop them. It's also illegal for them use the images for themselves whether you give editing permission or not..
My reason is very simple. Someone edits one of my photos. It looks much better, because I am such a bad photographer and a blind slug could do Photostrop, or whatever it is called, better than I can. I lose my job when the client discovers she can get better pictures, cheaper from someone else. I wallow in self despair, spend all my money on gin, and can't afford to feed the cats. Do you want two innocent kitties to go hungry? Well do you?