Why is there such a pressure to be skinny?

I don't get it. Yes, I want to lose weight and be fit since I am a little overweight, but I don't want to look like a stick. I don't understand why everyone is broadcasting that skinny is the only look that is pretty. I feel terrible for girls who are so down on themselves for not looking like an olsen twin. I know everyone has a different body and bone stricture, and genes...so why isn't it broadcasted that its ok to be yourself?