Hard to ignore someone talking behind you or texting in front of you in a movie. Hard to ignore the jerk who pulls out into the intersection as the light turns red for his direction, blocking cross traffic from going. Hard to ignore the people who stand in doorways and talk.
If you are able to simply ignore these morons, then more power to you. I, for one, grow more and more agitated every day with the complete lack of common sense and over-individual-bubbleness that plagues people today.
Someone above mentioned that it's because maybe we just don't like that people aren't doing things "our way", and someone else said it's because we are all smug and self-righteous. Sorry, the examples I listed above aren't just a case of someone not doing it "my way", or because I think I'm so much better. Those are typical examples of rude and ignorant behavior that have a direct effect on other people. Putting an item in a store back on the wrong shelf or parking in a no-parking zone are examples of things that may annoy other people, but don't have an actual effect. That's where being smug and self-righteous would come into play.
Well, yeah there are rude people in the world who don't think anything about others, but certainly not 90% of the them.