Personally, I’ve seen naked people that I wish I hadn’t seen. I thought they were pretty before I saw them naked. I also realize that some of them look like me. I have never been very good at realizing what I look like.
Plus, I have never been able to be naked without getting cold, or, if it’s hot enough to avoid that, I get overheated. I also have a hard enough time dealing with the fact that certain part of my body has a mind of its own, and will try to show off even when I’m not attracted to the person/people I’m with. And even nude beaches seem to make a big fuss over that.
This is why people do it. If the goal were just to be naked one could do that inside their house much more easily. To be nude outdoors on a nice day is a rush–not in a titillating way, but rather in a sensual way that is akin to jumping into a swimming pool on a hot day. The rush soon subsides, but nevertheless you stay in the pool because it’s pleasant to do so; IME being nude outdoors is a lot like that.
Being nude is an equalizer of the sexes in terms of objectification. Male fashion tends to be shapeless and modest, female (hot weather) fashions clingy or tight and as skimpy as the weather allows. For all the progress of women’s rights, this situation leaves no doubt as to which gender is more objectified by the culture, and which gender is not. Men and women both being nude certainly puts this on a more nearly equal basis. For me personally, in a nude swimming situation I enjoy the fact that I don’t feel pressured by social conventions to wear knee-length swimming trunks.