Well the way many of the items and weapons worked in the DS Zelda games needed touch screen. The Boomerang had puzzles where you needed to guide it along a certain path. You couldn't do that with buttons.... Well you could but it would be way easier just to draw that path.
Basically saying the game (if left the same) wouldn't work with regular controls, so the option can't be there.
Basically saying the game (if left the same) wouldn't work with regular controls, so the option can't be there.