system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are there only a slim variety of Chinese/Korean last names?
gpt
All the Kim's in Korea are self selected last names.   Until the 1890's no Koreans had last names unless they were royalty.   So then their Japanese overlords forced everyone to pick a last name.   

Kim's, Park's (Paks) and Lee's were some of the richest and most powerful royalty, so everyone picked one of those names, as they were the most badass names available.

That's why most people in Korea have one of those last names.