Why is it that some women who are fat of overweight try to squeeze into the smallest clothes?

Ever since it started to get hot, all the girls at our school have been wearing short skrits and shorts. I see the biggest girls trying to wear the short shorts that come to you cheeks. And the other week when there was a huge pool party at this girl's house, there were a look of girls who were big trying to wear bikini's and two-pieces. I'm not skinny myself but I'm not fat. I'm in the middle.I just have a big chest and a big . My stomach is flat and and my legs are fine..I've been working out alot.But I really don't like to wear short shorts or really short skirts because even when I wear a pair of jeans or sweat pants some nasty boy or dirty old man has to say something about how I have a "apple bottom" or they would call me "big judy" it's annoying and to make it much worse, I have a really big chest and I cna't really hide them either.That's why I don't really like wearing a two-piece to the beach because perverts stare at me and I'm only 17.