It would make the most sense having a server there in general. Get the population from that area, is what? Half the worlds population or something insane. Besides they seem to love their grindy games.
But no idea on the reasons they didn't. Maybe it's harder to setup a server there. Of course most probably wanna play it in their native language as well. Which really seems worth the money cost to break into that market.
Personally I will always wonder why they never put the server in Singapore. Surely that couldn't be so bad for Asians. Since most Asians seem to have a shit lag to both NAW/APAC. While being an Aussie I get, not a bad ping to Singapore either.