Imagine a world where cosplay photographers didn't just take pictures, but carried scissors and thread and wanted to make alterations to your costume and restyle your wig! Imagine some of them not being very good and you had no control over what they did. Shudder.
Imagine having to explain to your cosplay play community, "Well, my costume looked really good before this photographer messed it up."
I suspect after one or two botched efforts, you'd quickly decide on a policy of, "Thanks, but don't touch my costume or my wig" or "If you don't like my costume, make you own."
You might even start trying to avoid some of them, right?
That's how I feel about people modifying my photos. I like the photos the way they are. Please don't alter them, no matter how well intentioned or talented you are. Treat them with the same respect I show you and your costumes.
Welcome to the club
I don't allow myself to edit the photos either (other many minor exposure
and color correction). Those are the rules I set for myself. If you want
to edit photos in PhotoShop, buy a camera and take your own pictures.