I'm not so sure it is a limitation. Checkout this:
"Girl on the Rock" ........Photoshop manipulation of studio image by Ryan Rampton Photography Syracuse Utah
this next image is wholly CGI done with the idea that maybe we could create digital "Sets" and shoot with the idea of putting the live model into the "picture".
If it works with a minimum of work the next great fad in photography will meld living models with CGI backgrounds and characters.
More of my stuff can be seen at: http://modelmayhem.com/pics.php?id=15458