Akira Sakuma, game designer for the upcoming PlayStation 2 title Momotaro Dentetsu, commented in a Q&A session on his website about the welfare of third-parties on the GameCube in Japan. An excerpt is below.
Q: I saw that the homepage for Momotaro Dentetsu USA is open. Looking closely I saw the words... "PlayStation 2". There's no GC version...? That's hard to take as a GC fan, but I'm still going to buy it regardless. I don't think the GC has any issues as a console besides lack of disc space, but did you run into problems with that...?
Sakuma: I like the GameCube too; it's got better sound and disc response. But just like all the other publishers learned the hard way, the GameCube version just doesn't sell! The company can't put out something that doesn't sell. We could do it if the GameCube version sold at least 100,000 copies, but as it is now, I just can't do anything about it! I'd put Hudson in danger if I made them put it out without any expectation of making money!
For reference, Hudson released the two prior versions of Momotaro Dentetsu on both the PlayStation 2 and GameCube.
Thanks to Video-Fenky for coming upon this bit of info.