It may be a natural fit for the iPad, but it isn't a natural fit for humans. Wasn't that the whole point of the iPad?
I also look at my dad's fingers, which have enough thickness that he can't comfortably press buttons on smaller devices. I have girlish hands :) so I can manage it, but really ... you're actually implying that we should throw away hundreds of years of using a pen?
I've never used a desktop or laptop with a pen. I've never felt one was missing. I recognize the value of pen input for graphic designers (among others, no doubt) but the world has found a way to suit those people without baking the pen concept into the core design of the computer.
I also wonder if the lack of a stylus alone would make the same difference for him.
Or maybe a built-in keyboard is what he really thinks is a necessary element. I wouldn't agree with him, if so.