Anyway, my point is that you have to balance the burden of BC against its market value. For Wii U, the burden is very high, as you would have to include a PPC processor and a controller with a screen. These together (particularly the screen) are going to cost you a lot. Conversely, the market value is very low, as not that many people bought the Wii U, so the demand for a device that plays those games isn't going to be very high.
In post-NX devices there would be a significant market value to maintain BC, though, as they're trying to establish a multi-device software platform like iOS or Android, and being able to bring your software with you from one generation to the next is an important part of that. There's actually far more value to be created by Nintendo creating hardware that will be easily incorporated in future devices, than there is trying to create hardware than incorporates the Wii U.