As a conspiracy theorist at heart, here's my take - the vast majority of males who make decisions in the fashion/modeling industry are gay, and they have a skewed view on how a healthy woman should look.
There's a definite disconnect between the body shapes of the models who walk down the runway in Paris and those that entertain the dreams of Joe Six-Pack.
Askel, I flagged you because, IIRC, you're one of those who subscribe to my conspiracy theory.