You're not supposed to jerk off to the human, you're supposed to imagine you are the human. I know some people have difficulty doing that, but for me it's really easy and it puts me into the scene like nothing else.
When I see human female x scalie, all I can think is "am I supposed to be looking at her, or ?" I guess lots of guys maybe want to be the dragon fucking the woman. It's still aesthetic, but less sexy for me personally because I really just want to fuck the dragon, and I'm not female.