I dunno...

Someone kindly pointed out that it's hard to take a photograph of something that does not exist in real life (e.g. a dragon.)

I would like to submit that, in some areas, it would be a lot less expensive, less morally complex, and far less of a communications hassle to do it in photo-realistic CG than in real-life. Some things that come to mind: pornography, historical re-creations, medical images, things like that.

All that said, I don't consider photo-realism to be an end-all be-all of art. Quite the opposite in fact. There's room for all types of art in the house, yanno?