"But by far, most businesses still need laptops and proper desktops to work. Sometime you need a big screen. Most of the time you want to have a keyboard, a good one, to type fast. You want to have the precision of the mouse of do things on screen."

Absolutely, I need those things... for about 15% of my working time.

I suspect lot of people in roles where access to information is needed with minimal modification or addition to the data could work with other devices.