Lucumo: Yeah, Japanese companies (unsurprisingly) generally don't know about GOG and unless they have a competent Western publisher, they will only go for Steam.
They would probably also be more open to publish DRM-free, considering Japan has DRM-free stores (although it's mostly doujin stuff).
the_importer: Ya, I sort of deducted this a while back.
1/3 of my games on GOG and old titles, 1/3 are from Falcom and the rest are newer indies. On Steam, it's mostly Japanese games from Square-Enix, SEGA, Capcom, Marvelous, Namco-Bandai, etc..
Well, not offering any Japanese language support doesn't help in that regard, especially with them focusing more on PC these "days". I was pretty surprised when Dragon's Dogma: Dark Arisen hit the store.
If Sega would start releasing their stuff here, I would definitely become poor. But hey, they not only use Steam as DRM but also Denuvo, the worst.