Great Question.....!!!!! You get a star.
I think it all falls under the same reason as why Americans aren't allowed to die and they are allowed to sue when anything goes wrong.
Some (not all) Americans have grown numb with real life. We are uncomfortable with our humanness. We hide between rights and wrongs, black and white, rules and violation of rules.
In the hospital, we expect all efforts to be done to save a life, even if there is no quality of life anymore. We want everything no matter the price. And we think that we deserve it all rather someone else getting it.
How does this relate to nudity? Having a simple view of the world, complete with recognition that we are simply human beings made of flesh and bone, would be acknowledging that life is temporary.
We hide behind clothes and rules that say nudity is bad. We believe that our natural sexuality is bad. And we judge those that think otherwise. To believe that the body is beautiful and natural is to believe in being human. We would prefer to be gods and invinsible.
Nudity is being closer to human. There is nothing wrong with it in the appropriate location. Yes, it can be sexual in nature because all animals are sexual. But nudity is more than that, it is acknowledging the beauty in nature and being in touch with our temporary possession of youth and life.