Skinny girls want curves, curvy girls want to be skinnier - everyone wants what they don't have and there are benefits to each - as long as you are healthy.
I get very frustrated with the damage to young girls and women from using models who get further and further from a healthy woman's body with every passing day, then digitally altering them to be physically impossible.
Eating disorders are rampant and are unfortunately becoming worse, affecting a wider age range, and becoming more of an issue for men too.
P.S. Girls - whatever you think a guy thinks is the ideal weight, add at least 10 pounds. (20-30 if talking about a model. ;-))