The Wii U pad has the very unique position of having never being available for purchase separately. So for the 13.56 million units sold, there are 13.56 million

The Wii U pad has the very unique position of having never being available for purchase separately. So for the 13.56 million units sold, there are 13.56 million Wii U pads available. If it breaks then the replacement you will get will be taken away from a base console that may no longer work. So trying to build alternatives is a reasonable aspiration.