Both tinfoil666 and Palomine make good points.
I have some suspicions about the driving factors behind some of this.
An impression I have is that society seems to equate that
notable curviness -- pulchritudinous beauty, based on the classic female form, part of the essence of physical femaleness -- is somehow damaging to the modern ideal of the intelligent, empowered and capable woman. Thus dangerous to hang out there as a meme of the ideal, in modern media and discourse.
However, I observe that one can certainly have a killer hourglass figure and still be intelligent, empowered and capable.
The other side of my impression is that that much female power in combination tends to strike fear in the hearts of that same demographic shared by those studio execs and other "captains of industry" - and thus tends to get suppressed on that account also.
I think this is one of the reasons why the persona of the intelligent, powerful And beautiful woman often gets relegated to the femme fatale - Danger, Will Robinson!! Or gets held up as a sacred cow to get harpooned (how's that for a mixed metaphor? I'm not implying manatees here...)

- case in point Sigourney Weaver in Working Girl. But the writers softened (hardened?) that one by endowing her character with a "bony ass". LOL
Heh, the Working Girl illustration even works on the other side of the coin - Melanie Griffith's character, unpolished, curvier and alluring, achieves her goals with sweat equity rather than raw intelligence - wins. This movie worries me a bit -it's supposed to be an anthem for female empowerment, but taken at the levels I'm talking here, it's motives seem a bit duplicitous. You could argue this more than one way...
Anyway, despite efforts in various fronts to promote gender enlightenment, in large proportion across today's cultures the modern male still prefers his sex objects to not be particularly intellectually challenging. It's much less stressful that way (can you say, Sarcasm?).
All this boils down to avoidance of some tricky sociological undercurrents. Mix this gunk up with marketing, and the scale of investment and expected returns on big media like movies and television, and you have many of the ingredients for today's media.
I hope to see lots of Emily Barry, notwithstanding. WITHOUT forced weight loss or reduction.

-D'Artagnian