I honestly think it varies from language to language. Likely the problem with my application is that very few people actually need to lean Korean insofar as learning English is standard there. Sure, would it make me a better scientist in the future (journal articles with more international collaboration have been shown to be better articles) and allow me to more fluently collaborate with a country that is increasingly specializing in my field of research? Yes. Sure, my resume is bright and shiny and they have reason to suspect I could handle the program, add to the diversity of the group, etc. But do I need to learn Korean? No. I would suspect people who made the Korean cut would be those aspiring to do work into Korean history that requires that you understand untranslated texts and those in similar situations that really require it. I also bet Korean had one of the highest volumes of applicants -- no previous experience required, generally popular country, etc. Languages like Urdu, on the other hand, which, to my knowledge, aren't spoken by people who know English, would have an easier case to make...
Oh well. I'm writing up four applications to computer programming-intensive programs. Would likely do me more good in the future anyways... Though I still have never been out of NY and it perpetually bothers me that I cannot afford to fix that myself.
Good luck, guys.