That's an industry trend in general too, there were like 10000 games made for the PS2 but as costs increase the number of titles continues to decrease each generation. In this case they've probably decided they don't have the money/resources to allocate to making Wii U ports which will require a lot of optimization.
It's really Nintendos own fault, yet another underpowered console
Playing: Dark Souls 2: Scholars of the First Sin Watching: Mr. Robot