Once people buy the Wii, do you REALLY think Nintendo cares how much people play it??? The fact is, the "Nintendo" titles (Mario, Zelda, Metroid, Wii-Fit/Play/Sports) all sell REALLY well. And then you have some 3rd party games that do really well (like Tiger Woods) and then you have some gimmicky games (that cost $20-$30) so you don't expect as much.
Again, the audience that Nintendo is going for (for the most part) doesn't care. Yes, the lack of DLC for the first Rock-Band was dissapointing, for me. But out of the 10 other people I know who have Rock Band for the Wii ... they could care less.
You need to stop comparing the Wii to the 360 and PS3, as a hard-core gamer you don't "get it", and that's fine.