picture signatures

Could someone please tell me why I would possibly want to sign a picture? All it proves is that I had it in my possession -- it says nothing at all about if its been hacked (and indeed, it can be hacked regardless of what one does). A digital signature on a picture is no better than a court oath saying "yes, I took this picture". The only time you might ever want ANYTHING digitally signed is if you have doubts as to its origin or if someone might deny having signed it. It doesn't do you any good vis a vis verifying origin of a thing. .pm