People and I am sure, nintendo, are afraid that we are reliving the 3DS, which only needed more games to have sales stay high continuously. The price cut was a bad choice that made many angry. Ambassador games was not enough.
Plus they would not be making any money off of a reduced price system, and the boost in sales would be short lived. More Games!
The Wii U is in far worse shape than the 3DS ever was. The lowest the 3DS ever sank to was 97k I think in North America (for example), which is almost 3x what the Wii U sold last month. Prior to that short period where the 3DS price drop was announced but not effective of course.
A couple of more Mario games isn't fixing this mess alone.