Activision can lose money on a Wii U version they don't care the other versions will sell well enough. And all it ends up being is the same thing so it probably takes little time to develop. Little time, smaller development team, and somehow, solid sales means they wouldn't care if AW sold low on Wii U.
XBOX ONE/Wii U/3DS/PC
RIP Iwata 12/6/1959-7/11/2015
Thanks for all the great memories!