Tupin's right twice.

1) STAY ON TOPIC
2) Advertising sucked

Nintendo if people read up on some of their own pre-Wii U press stuff made it clear they had some supply line problems with the tablet controller to the point you can't buy a spare from them online nor at retail, just a few spares for warranty work until sometime in 2013. Since they were limited on those, no matter how many systems they make, you can't move them without the tablet controller. So in that, what reason would anyone consider it a good idea to advertise the hell out of the Wii U like they did for the Wii after what happened with those Wii sales explosions all through late 2006, 07 and early 08. Even with it out now I haven't heard much for them doing print ads, and I've only twice ever spotted a tv ad that shows a game and says Wii U on it showing the system in use. I remember seeing Wii ads when it came out like it was an election year.

Lack of advertising really did it, they went with just going low key really online allowing the Nintendo super fans to know it exists and to get it, but let it stop there probably to avoid some form of another Wii 2006 push when they knew they couldn't back up the demand with product.