This game really shouldn't be viewed as an attempt to sell systems, at least not on its own. Wii Sports U is part of the growing collection of socially active games. Such as Nintendo Land, Wii Party U and to an extent NSMBU. Together these games sell consoles to a certain audience.
I think the business model here is well thought out. Just $2 to try out the full game for a day, get some friends over and that becomes a real cheap way to spend a maybe otherwise uneventful night. I don't game too much these days and don't have many friends who do neither but I know we'd all be up for that. Now it just needs to be fun enough to justify paying $10 for one sport.
The online multiplayer is really where this game will/should shine. I have a feeling it might start off slow but as more and more people start getting involved in the clubs and competing for better scores and higher ranks it could grow immensely. A spectator mode could be a nice addition. Watching the 2 top ranked players boxing against each other for the top spot could be interesting, then use the gamepad to take pictures. Might be asking a bit too much :P .
This could serve as perhaps an introduction to online multiplayer for people who'd otherwise never experience it, if Nintendo can get everyone interested.
(edit: I kinda failed at completely making my point about why I think this game is a good move by Nintendo cause reasons, maybe I'll try again later :P )
