Well, that requires a lot of kids being addicted to playing games first.
I'm guessing there just isn't enough public interest in order to justify investing in eSports. The lack of public interest could stem from culture and how society views video games. You have the more conservative (is that the right word?) Asian style of upbringing. Cram school, lots of school and homework, good grades, and then university and finally an office job most likely. Also, I've heard that there are less internet cafe's in Japan. This could be because of the readily available PC's at home, and just because they don't have a culture for it like Korea. (I honestly don't know how PC Bangs got so popular in Korea. Is it because of the starcraft boom and it just became popular? Idk. In China it's because there are a lot of poorer areas, and going to an internet cafe for 5yuan - 20yuan [$0.70USD = 1 yuan approx.] a day is cheaper than buying your own rig)
Edit: They have a huge fighting game and Nintendo scene though. Like tekken, street fighter, smash, etc. They have a lot of arcades.