Comment by kijin

Korean age is a hack that helps ease the friction that all those rules of seniority and different speech levels impose on us.

It gives you an age bracket within which everyone is equal, once and for all, regardless of their exact date of birth. Your friend isn't suddenly going to speak down to you when he turns 7 and you're still 6, except perhaps as a joke. Both of you are 8 in Korean age, and will turn 9 at the exact same moment. This age bracket produces a stable peer group who can remain friends for life, regardless of when or where individuals went to school, got a job, or enlisted in the army -- all the other places where hierarchy can be imposed.

Of course, the year is also important for reasons of superstition. There are still some elderly people who ask for the (Chinese zodiac) animal associated with your year of birth, instead of the year itself.