I don't think anyone has ever run into DRM on pictures. Once polaroids became popular, everyone had access to photography which meant that there were few large corporate interests to run propaganda campaigns. There is a clear line between Hollywood films and home movies and I suspect that very few people would feel bad about sharing home movies without the consent of the person/family in/recording the movie compared with how many people would feel some kind of guilt about sharing a feature length blockbuster. So the attitude of the creators and the diversity of creators seem to play a large role in determining public acceptance of sharing certain things.