I don't know how to respond to this one.
On the one hand I'm about an American size 8 (which is an Australian size 10 which is an English size 12 - confusing, I tell you!) which makes me neither fat nor thin. I'm towards the low end of my healthy BMI range, but I still have boobs, a belly and a bit of a wobble to my thighs when I strut my stuff. I go up and down about how I feel about my body, but I'm generally OK about it. I have curves, I am not meant to be skinny (been there, done that, got the medical problems to prove it).
My two best friends from home would be US size 0-2 at the most. These ladies eat, drink, and do all they can to gain weight, to no avail. They don't wear revealing clothing, and actually have great problems buying clothes as the only styles made for their sizes are the ones you mentioned before. If they don't want their stomachs or 95% if their legs on display, they don't have a lot of options. High on their list of priorities is covering their protruding collar bones and bony knees.
I know that 'fat chicks' get a lot of flack. But I have never seen anyone receive such direct, steaming vitriol about their size as these girls. People tend to snigger about 'fat' people behind their backs. As being skinny is seen as an afront, yet not one that you need to be PC about, people have no problems telling these kind, intelligent, sensitive, funny ladies that they are indeed the spawn of satan because their hip bones protrude.
Yes, I can see how life should be easier for the skinny girl, but just as all fat people can't be pigeon holed, neither can the skinny ones. They want to have breasts and hips like me, I want to have a flat stomach like them. The sooner we learn to love diversity, the sooner us women can stop being such horrible f**king cows to each other and get on with things.
Some people blame the media, some blame men, I blame us. Skinny, fat or perfect, we're always managing to find new ways to bitch about the other camp.