I'm not saying it's right. It's some serious prejudice.
I'm saying that the sponsors and event organizers and TV people decided they'll make MORE MONEY with MORE AMERICANS in the top 10. It's that simple.
If they wouldn't, they certainly wouldn't be doing this. They probably fear that in 5 years, 95% of the top golfers in this American sport, on American TV, won't be American. Hard to sell that to sponsors.
Whatever the reason, they did their reseach, and believe it'll be more profitable without the S. Koreans.