I'm not familiar with that community or even ones closely related, but I've worked several years in Japan and Korea, so I'll take a stab at it.

For Japan, I'm pretty confident it's the language barrier. As in most countries, tech people in Japan are mostly males, and mostly are not very strong in the humanities and in social skills. This group tends to be extremely self-conscious about their limited English ability and generally avoids interaction with foreigners.

For Korea, I see a trend, but I'm not confident about the explanation. I see lots of bright kids at university, see them get hired at big tech firms, and see them enthuse about their work over beers. I don't see them interacting a lot with foreigners. My impression is there is so much going on within Korea that they don't feel strongly motivated to look outside.