American doesn't know squat about seiyuu.
I know mad amounts about seiyuu, being a game and anime seasonal anime otaku. I still think it wouldn't be worth it though, since the voices in the demo sounded fine anyway. The quality of Japanese voice acting is always wonderful even in some of the more "novice" people, because seiyuu over there take classes specifically to do it, and the direction is often very good.
It's more of a notoriety issue. I mean, a lot of people would be considerably more excited to have dinner with a celebrity from a huge blockbuster smash hit movie than someone from an obscure B movie. I don't count myself among those people, but the average person probably applies to this statement. So CF can't really
market the voice-overs here in a way that would justify any decisions that costs them mega monies. If people who are popular in western culture are included, they could make money off of that even if the individuals in question sucked. Just because of the power of fame in and of itself. It's lame, but it's also reality...
Summary: I agree with you for the most part (I hold high opinion of Japanese voice work-- though to note I hold English voice work to a variably high regard as well), but - sadly - the market and the world is what it is regardless...