There are many delicate social norms that might be completely foreign to those come from the West. The way a simple 'hello' is exchanged is different when you do it to friends and to parents. It might be shocking to find how an 'age factor' is so predominant in Korean culture. True, I'm particularly more prone to pay extra attention to culture and language in general, because I do translation from English to Korean, or from Korean to English.
If you're talking to someone who was born even a year earlier than you were, it changes the language structure you are allowed to deliver, let alone your attitude. (This gets less strict for older generation, but it is almost an unchallenged rule to younger generation.)