Psychologically, why do we care so much about looks?

the whole world revolves around looks. even in middle school wearing the wrong shoes can you get out of the "in" group. so the question is why do we care so much? i mean why would we choose someone more attractive over someone less attractive. the reason is we think that hanging out with the more prettier people can help us become more popular or more well liked. which most people are wrong about. people only care about looks anymore and i am so sick of it.