who says korean do not ask age?
Asking age is very common in korea so many koreans ask age in western countries easily without realizing that could be somewhat rude...
the moment when you are born is already counted as one year old in korea and when you pass new year, you get one year more.
For example, if you were born on 31st dec 2000, on that day you were 1year old, and you became 2 year old on 1st 2001.
So, you lived only 2 days but can be already 2 years old.