Nintendo's new gimmick

Nintendo has recently announced an accessory for their Wii console that significantly improves the motion control offered by the Wii remote. The accessory is basically a few extra accelerometers that attach to the bottom of the Wii remote. Via IGN:

The good news is that Nintendo is on the threshold of changing all of that once and for all thanks in whole to a little attachment that plugs into the bottom of your Wii remote. It's been coined MotionPlus, but we prefer to think of it as an integral ingredient -- that little something that's been missing from the Wii remote all along.

MotionPlus will come bundled with Nintendo's newly announced Wii Sports Resort, which ships next spring. No price point has been announced. The Big N pulled back the curtain on three games featured in the soon-to-be-gatrillion-seller, including Power Cruising (racing a jet ski a la Wave Race), Disc Dog, in which you throw a frisbee to a canine, and Sword Play, a sword-dueling component that has us excited for the future of the Zelda franchise. In short, MotionPlus is no joke and it's going to dramatically change the way Wii games are played. As an aside, Shigeru Miyamoto has already hinted that MotionPlus may be packed with all Wii remotes in the future.

My question is: why in the world was this not included with the Wii in the first place? It is unlikely the technology did not exist two years ago when the Wii was first released, and if they knew they could get the control response to be 1:1 (with your hand movements), why not do it right the first time around? This would have made the technology all the more impressive to the consumer and also allowed developers to produce higher quality games. Seems fishy to me.

That said, I think this accessory will make the Wii all the more successful.