[Suppafly]

I think part of it is that he made such a big deal about saying the monkey took his camera and took the photo, to drum up excitement about the whole thing, not realizing that the rest of the world would use that as an excuse to publish his photo without giving him credit for it. I'm not even sure the monkey actually took the photo itself, but the story that made the photo popular has been the story for so long that he can't walk it back now.