People are posting on the intertubes about hardcore gaming and all. Eh, the truth is that even though I'm excited about getting FFXII: Revanant Wings, and am squeeing about it, and am also excited about Civ revolution and Spore: PC, that doesn't mean I'm going to put down folks who want to use their ds for a diet helper[there's really a game like that!] Really, it's all capitalism. The amount of people who want to spend even 30 hours playing a game is much smaller than the amount of people who want to play something for 10 minutes or so, and then put it down. If Nintendo can collect money from those folks, of course, they'd want to.
Of course, I'm so behind in my gaming that there are enough not so casual games on PC, PS2 and DS to have me playing for at least 5 years, so even if Nintendo only released Sudoku games for all its systems for a year, I'd be happily gaming away.