Nintendo says it dropped Gamepad support for the Wii U version of Breath of the Wild to ensure parity with the Switch version.
Oh hey, The Legend of Zelda: Breath of The Wild, launched for the Wii U at the same time as the Switch, did you know? The older console's version is understandably undershadowed by the shiny newness of the Switch, but Wii U gamers who have been keeping an eye on the game since it was first revealed as Zelda Wii U back in 2014 will notice the absence of a feature. The Wii U version of the game does not support the Gamepad in any way (except as a second screen), despite early trailers of the game having players use the Wii U's unique peripheral as a kind of permanent inventory/map screen.
Nintendo's Hidemaro Fujibayashi explained to IGN that developers "aimed to provide the same gameplay experience across both on Switch and Wii U," noting that when development began, well before the Switch was announced, touch screen features were present.
"In doing our testing without the touch features," he said, "we noticed looking back and forth between the GamePad and the screen actually took a little something away from this type of Zelda game."
"Without the touch features it actually turned out to be a really strong gameplay experience," he explained. "After more experimentation and testing out, we realized that this is the best way to experience the game. That's how we ended up with the current gameplay style in the production version."
So that's why Breath of The Wild's Wii U version doesn't feature the Gamepad.