However, I think that the photo thing is weird because how do they know what you look like anyway!
True.
But it would, presumably, be harder for someone to find a pic to steal of a person with the identical bag, on the Internet (with a recent date); than it is to steal pictures of a bag on its own.
I think they think of it as a way to cut down on the likelihood that you are selling a bag that doesn't exist and therefore, won't be delivered to the buyer.