do looks really matter?

I really wonder what the true answer to that question is. Do our looks really matter when it comes to first impressions,job interviews,random meetings, etc. Why are we as humans not allowed to dress how we want, when we want without the fear of being judged by someone else. Just because a woman has all her cleavage out, does that give the impression she's easy? And if so, why? When its 5pm and a guy is walking down the sidewalk in plaid pajama pants does he look lazy? Why do we think this way? Why do we have to put our best clothes on to go to church? why do we have to wear a pressed white shirt and slacks to a job interview? Just questions on my mind. There could be answers, but do they really matter?