Simple niceties such as ... basic manners, are a lost art, usually reserved for the intelligent, non-slackjawed, non-furrow browed individuals that don't continuously drool all over themselves while struggling to comprehend the information their eyes, too quickly, transer to their brains.
Think of it like that, and everytime someone is rude, you'll laugh a little imagining them struggling to tie their shoes, or trying to remember which lung breathes first.