Well let's see, based on everything I read it seems I am not alone in referring to human nature when discussing the subject of being judgmental, ZenHabitats referred to this as being part of our own human nature make up. We are all guilty from time to time of judging another person or situation without knowing all of the facts.
From a person feeding a family of five on one online income to that mom in the grocery store with the screaming child, we all have that moment where we either criticize the way they live or how they parent, we judge them in a negative light without having ever lived a moment in their shoes. Then we have the people who just insist on making other peoples lives more miserable or sound worse than theirs to avoid looking in the mirror at their own self to fix their own issues.
It doesn't matter why a person judges but honestly, this quote says it all for me,
No accurate thinker will judge another person by that which the other person's enemies say about him. -- Napoleon Hill
So please remember, it's common to judge situations and people at first glance, but when you make a habit out of it, well then maybe you should take a moment to think harder before making that judgment and take a long hard look in the mirror at your life and self.