Could the fact that we need a toplessness movement to ensure women the right to go around topless if they want to and the troubles this movment is having making headway be due more to economics than the usual culprit, prudishness? Nudity is highly controlled on the big and small screen as much as it is in Real Life. One factor is that actors and actresses have contracts with the studios specifying how much they will or will not take off and what they will or will not show to the camera [find an excerpt]. It costs more to get a big-name actress nude in front of the camera. By the same token, if a well-known actress is nude in a film, that film can potentially have more draw than otherwise, i.e., the film makes more money.
Supply and demand. If nudity were commonplace in society, the money which actors could demand for contracts including nudity would be dramatically decreased, in fact, nudity would be expected as part of any regular acting job, just as it is in France, Germany, Japan, and elsewhere, i.e., no extra contractual consideration. Also, films containing nudity would have no extra draw, earning power, than those without, i.e., no economic boost for nudity in film.
So, as usual, Americans love their prohibition. It looks on the surface to be motivated by prudishness, but underneath there is the economic realilty, the price inflation, the increased demand, and the people involved in the trade (and in the enforcement activities surrounding it...?) getting really, really rich off of it. And, of course, lots and lots of people getting hurt. More crime, more human degradation, denial of physical and emotional needs and so forth. We've seen it with the prohibition of alcohol under the Volstead Act in the 1920s, we're seeing it now with the "Drug War" (should be renamed the "drug public health initiative" and phased out) and it may well be the case that we're seeing the same thing with nudity.
There are telltale signs: police enforcement activity against something that really harms no one, a lot of money moving around, artificially heightened demand/interest, etc.
The film rating system makes it explicit (so to speak), i.e., which films have nudity and which do not.
One question which would be a real clincher is who is lobbying for and against all of this stuff? Is the Film Industry (or somebody related) really pulling to keep all of us from getting our togs off at the park or wherever in order to jack up their own profits?