Somebody explain to me why being popular is so important?

So I'm a junior in high school and I'm in the top 10 of my class,I play softball,and I volunteer in the community. I pretty much get along with everybody.I talk to everybody ,even the ones who students don't generally talk to. But it really hurts to hear freshman say they are gonna have sex with some popular guy just so they can be with the "in" crowd. I don't put myself in a clique , I'm a all around person.So why do people think being popular is the best way to get through high school.