It's not about them though, is it?
It's about all of us "normal" women who feel fat and enormous for being normal. Who always feel we should aspire to the likes of kate and pippa, and fall down miserably because we don't have the time and money to put into our bodies. We feel like we should be making more effort to lose weight, get to the gym, and be closer to the "perfection" of these women.
How many threads on here have we read where women have no idea of the correlation between weight and looks. One day you'll get someone asking if 9st at 5'6 is fat, and everyone replies that "ooh, it's not overweight, but I'd feel flabby at that weight". Then you get a thread the next day about someone being too thin, they're 5'6 and only 9st.
So we look at celebs, and guess their weight, so we can hold ourselves up and compare, and guess how much weight we have to lose to be perfect. It's classic eating disorder territory- if i could get to 8st like pippa, i'd be as thin as she is.
Once you lose the advantage of youth and hit your 30's and beyond, the pressure is even bigger.
Men just don't have that pressure to be thin and beautiful. They are not valued for their looks, they know they will get the job/be treated with respect/ not be abused if they are carrying that extra stone or their hair and make up isn't perfect. Which is why men aren't posting similar threads.
It's society putting thin and beautiful on a pedastal above other femal attributes. Who knows what pippa studied at university? Does anyone compare their own degree and deem it better/worse? No, because society doesn't care.