I think it is in part because most persons who finally become comfortable with their own bodies are usually older. When it comes to persons whose may be a bit overweight, I think that is more a reflection of a society that is mostly overweight.

In any case, for nudists/naturists the point of beign nude is for one's own enjoyment, not be to seen or looked at, or for the enjoyment of others. Among nudists/naturists they/we are generally more accepting of people for who they are, versus who or what a trendy society wants them/us to be.

Nudists/Naturists are the most accepting and least judgemental group(s) of people I have encountered in my life. You are not judged for how you dress (obviously), who you know, how much money you have.

There is a bit of a split when it comes to "swingers". The majority of nudists/naturists believe in family friendly nude recreation, while swingers tend to make their lives all about sex. Generally, nudists/naturists don't like the swingers, but often have to tolerate them. And, BTW, swingers are no more attractive than the nudists/naturists.