I don't understand it. At home, if you walk past someone and make eye contact, you smile or say hello. It's just something you do. I'd like to consider myself an intermediately experienced traveler, and in my experience, most people that I have encountered at least smiled at me when we made eye contact. This is NOT the case in Korea. Koreans are too busy living their very busy lives to be bothered with something as menial as a smile. This is unless of course you are an ajumma or ajoshi and feel the need to crank your neck to get a good long look at the waygookin with the big boobs!
Most Koreans walk along with their phones permanently attached to their ears via earbuds and shut out the world. I walk around with my music blasting in my ears too, but I don't let it distract me. What stumps me more than Koreans not acknowledging others, is the fact that other foreigners don't acknowledge each other. Is it really that troublesome to give a smile or say "hello?" Are you so miserable here that ya can't recognize that someone from your corner of the world is walking past you? Are your facial muscles too tired from teaching bratty children all day? Maybe I'm asking too much, I dunno. I just hate those awkward moments when you see a Westerner approaching you and you don't know which way to look. Should I look at her? Should I look away? Down? Where?!?!? Is it too difficult to just give a fellow human being who is in your shoes a small smile?
I think many people come to Korea thinking they've found something new. They're gonna go teach English in a country where no one has gone to teach English before. Maybe going to teach in Korea is a big thing in your small town of East Bumfuck, but in the big scheme of things, you're one of thousands, Bud. In fact, you're one in about 20,000. Smoke that, you pretentious asshole! :)
They learn that they are one of thousands as soon as they get off the plane. From then on, they develop this icky persona that screams "I honestly believe I'm better than you." They will only date Korean girls, they study Korean like crazy and then feel the need to correct you in public when your Korean is wrong, they only drink in Korean bars, they wear skinny jeans and black rimmed glasses without lenses (a dead giveaway that this person will not be of any interest to you), and they talk to the Korean staff more than the foreign staff. So to those dumbasses, I say "Get off your high horse and come down to reality with the rest of us lowly foreigners." And to the rest of you, SMILE when you see someone walking by you, you just may make their day :)
Love you all!