There was a study a while back stating that only a very small % of console owners owned more than one of the 3 current-gen systems.
If:
(A) The software available sells the console
and
(B) the AAA 3rd party titles are available on the X360/PS3 and not the Wii.
then
(C) there's an implication that the demographic interested in the majority of AAA titles (which tend to be targeted at a very specific demographic) own a X360 or PS3, and NOT a Wii. As such, The number of available buyers, for your typical AAA title, and in the Wii's demographic set, is likely lower than it is for X360/PS3 -- especially if you combine the latter two platforms' owners as a potential audience.
That alone explains why there are no AAA "gamer" titles available on the Wii, and even if the Wii hits 50% market share, then by nature of there being no AAA titles for it (other than Nintendo stuff), there are going to be far fewer current Wii owners interested in those kinds of titles.
You buy a console for its software. Some may find it hard to believe that Wii owners *want* billiards, poker, etc., or Nintendo titles only, but... The Wii is selling like crazy, and there's supposedly not much system overlap. I find it hard to believe that a whole bunch of would-be Wii gamers went and purchased a Wii in *hopes* of getting some AAA titles. If they wanted typical-demographic, AAA titles, it seems likely that they went out and bought a X360 or PS3, and *not* a Wii -- buying a system in hope of their being some 3rd-party "AAA" titles for it someday is... not something any buyer is likely to do, in any situation. Because the Wii sells alot, says nothing about its demographics, but the titles available for it, and its higher-end competition, and the relative lack of overlap in console ownership does say something. I would say that, because (A) above is pretty well accepted as true, that Wii owners are actually, as a majority, *not* interested in AAA games, but instead are much more interested in Nintendo games and license titles from movies, etc -- i.e. the titles it has available.
Wii Sports? Win. Wii Play? Win. Wii Fit? Win (or soon to be). Wii Call of Duty 4? No, and the publishers seem to agree. Putting CoD4 on the Wii would be like M$ bundling a AAA shooter in their Windows Game Packs -- it just won't be popular in the common demographic, or so the history of "casual gaming" tells the publishers. Sparkle Gems Puzzle Treasure Finder 8? Super Vegas Reno Ultra Blackjack Bet-it-all edition? Oh yeah, those are popular -- and they doesn't require much investment either.
Thus the publishers aren't "dumb" for not spending AAA title money on the Wii. They're targeting the intended audience, on the intended platform. Anyone who thinks otherwise, apparently believes themselves a lot brighter than an awful lot of well-educated busniess folks who run those companies... any failings those companies are currently undergoing probably has way more to do with the bad recession in the US than the publishers being "dumb".
