Because usually there's absolutely no reason to do so, because it's static and you you have the layout in muscle memory.
- Because staring at your keyboard isn't great for your neck.
- Because when I'm typing I'm outputting my brain into the computer, I'm not trying to take in input.
- BECAUSE YOUR HANDS BLOCK THE KEYBOARD.
The mouse is more of a follow and enter type of interface, as is touch. Keyboards are a high ply (eg 102 keys + shifts) with chords and chains, in that a you generally hit a series of keys to do something (typing) and not a single button. So massively more options than the 12 they can get up there on the top row. So memorization wins out in my mind here.
Where I think this would help is when you're learning new things and have to move your hand to figure it out. Like say a new character in dota... but again the monitor is better.
This keyboard looks cool tho. Tho wish they'd put some non-mac pics up.
I don't see a use case for this though, I rarely look at my keyboard.