Hello? Hellooooooo!!!! - or How Rude!

Is anybody out there? No? Well, okay then. Now I don't have to worry about posting anything interesting or sounding intelligent. Gosh, I probably don't even have to use grammar... Then again, the prospect of such freedom is scary, so I'll stick with the grammar for now (It'd be like running around the house in your underwear when no one else is home. It still feels wrong).
Which leads me to my thought of today: Cultural mores (pronounced "mor-ay") and folkways. I think it's funny that we come to believe that certain things are wrong and others are right, without ever questioning why. To be fair, many of the things your parents taught you as you were growing up are "right" and "wrong" for good reasons -most often to avoid conflict and show respect to others. Then again, if we never take the time to ask why we do or don't do things, why some things are and are not socially acceptable, we end up with manners and practices that really don't make sense (and perhaps are simply inconveniences).
The best examples of such pointless social rules are often realized when submerged in another culture. The clash of cultures and the misunderstandings that ensue often force one to contemplate why they ever did things in their way to begin with and why the alternative is (or really shouldn't be) acceptable. For example, I have an American friend who's living in Paris (a pretty culturally-compatible place for Americans). She once recounted for me an episode during which she dropped her passport on the metro and couldn't find where it had fallen. A passport is a pretty important thing to lose while in a foreign country, and her consequential distress at her inability to find it was understandable. She was getting panicky, after a few minutes and was down on her hands and knees looking, asking everyone near if they'd seen it. However, everyone on the subway was completely ignoring her, despite her constant "I've lost my passport!"
She initially thought that all these Parisians were simply cold, rude individuals, but upon telling her French friend of the incident, she learned that the people on the metro were trying to be polite. Had she said, "Can you help me find my passport?" any decent person on the train would have tried to help, but since she was only exclaiming how she had lost it, they did what they believed was the polite thing and completely ignored her. The reasoning behind this behavior was that they didn't want to embarrass this woman in her distress, and so they refused to acknowledge it. This response is a far cry from what many decent Americans would do, which would be to help the poor woman find her passport (hopefully), so she simply thought these strangers' refusal to even make eye contact with her was just rude.
And so at the risk of this question echoing as it bounces off of the empty walls of this blog... Can you think of any manners or customs that you've been taught that don't make much sense when you stop and think about them? Have you ever been confronted with a different way of doing things -whether in a different household or a different country- that has ever seemed wrong or made you question the way that you do things?