This is something I have always wondered about and confess I am the same as anyone else.
Once you have seen a naked male and female that has gone through puberty, then you have pretty much seen every naked person on this planet. Of course people are different, but you can look at a persons build and guess what they look like naked, ditto with a woman's breasts, they may be hidden under clothes, but their size is not. The only thing that breaks this rule is that men hide there penises under clothes so you can not make an evaluational.
So why do we love to be or see nude people?