This leans towards a few short sighted trends.
(TL;DR below.)
Some women feel that having female skin shown to "strangers" is akin to taking advantage of the gender.
(This is evident on a smaller scale, when you see a woman in a short skirt in public. If she catches your eyes on her, even if you were only looking at her to make sure you didnt bump into her, she can shoot you the dagger-glare, and youre pretty defenseless against it.
The rub here, is that she does want SOMEONE to notice her, its just not YOU. This can bleed over into other forms of media, like videogames.
Showing female skin is only ok, if the female in question has consented to each and every set of eyeballs present. Anything less is 'demeaning' and sets the gender back.)
Another way of looking at this is that nudity =/= pornography in a surprising number of minds.
This is also why there are typically age-limits on pornographic material.
Lets be totally honest. No matter what sort of scripting and 'talent' (bowchikawowwow) someone has on a porn set, it all pretty much boils down to a masturbation aid. Dare I say it... an object?
Porn isnt interactive... if it was, it would be sex. And if you were exposed to porn at a young age, without the tempering social-life (school, being a primary example) balancing your ideal of what a girl was, then you could very well grow up to believe that women were just that. Masturbation aids. Not people. And thats a road that too many Jeff Dahmers have traveled.
So age limits on porn (remember, porn =/= nudity to many) help us ensure that people grow up with their ideas balanced.
TL;DR: Nudity has age limits to keep boys from growing up objectifying women.
Whiskey Echo!!
Mythgraven