Why are so many girls willing to hurt themselves to become thin?

I know it has a lot to do with media, but I don't understand why being super skinny is being the "right" size? We have stars starving themselves and setting a terrible example. What happened to stars being happy with their curves like Fran Dresher, Queen Latifah, Beyonce, etc. I know I think skinny is beautiful, but the skinny I'm talking about is what looks right on my body. I am Hispanic and take after my dads side of the family which tends to be thicker and heavier set. I know I have a wider bone structure than other girls but its who I am. I think for me to look beautiful I need to look healthy for my height and body shape...not like a Megan Fox or an Olsen twin. Why do a lot of girls want to become really skinny instead of trying to get to a healthy size?