Why people judge?

One of my friends recently gave me a negative feedback on my appearance. Usually, I wouldn't have cared because of the obvious male fan following, but this time, it hurt. He almost told me that I am "not good enough to have a second look". OMG. At first, it just hurt, but later while my pain subsided with positive thoughts infused in my head forcefully, I realised, why did he need to judge me? After all, I am just his friend. Judging can be so disturbing. It creates its own vicious circle. So first he judged me, then I judged him thinking "he is manner-less" and then, my another good friend judged me for "judging him" and concluded that I wasn't any different than him. The point is, if judging is so painful and uncomforting - WHY JUDGE?