There are Wii U ads. However, they are mostly on specific websites, and channels when children's cartoons or family programming are playing. For example, I have seen Wii U ads during WWE programming. I've seen them on Nickelodeon. Etc.
They do need to put their ads on more prime time slots. But at the same time, less people are watching TV these days, especially younger folks. So having ads on Youtube, etc., is not such a bad thing.....
No one is arguing though, that they do need to have more ads.