You're starting to sound like one of those funny infomercials where everything is black and white and the actor fumbles with some overtly awkward action, that is otherwise mundane... Holding their outstretched arm up over their head with their other arm, a grimace of strain on their face, trying to scroll with their pinky finger. All the while the voice-over is asking why you'd subject yourself to this.
It's a, very natural, quarter inch movement of your thumb while your arm rests comfortably on the table. Not unlike having your hand on your coffee mug.
I think the point, though, is that your hand wouldn't naturally rest on the table near the screen like that. The main reason you're comfortable doing that is because you know you can scroll with your hand in that position. The natural resting position would be to relax your hands off the keyboard after typing and that puts it squarely in the area of the (comically) huge trackpad.
I'm reading this right now (well, thirty seconds ago, before I started typing) on a touch-screen Chromebook. My right hand was resting on the table in a vertical orientation with the edge of my hand on the table, my finger loosely resting on the back of the screen, and my thumb on the touchscreen scrolling up and down. Very smooth, very natural.
Conversely, scrolling up and down this text box using the trackpad is tiny, cramped, constrained motions of my finger on the touchpad.
Except that the mouse is an example of being completely unnatural... The whole point of the positioning on the trackpad is that it's right there when you relax your hands from the keyboard. Otherwise, you'd see computers with trackpads above the keyboard. The positioning of a mouse may be a reflex from usage, but it's the exact opposite of natural.
Bingo. Your hand is already there, no need to leave the workspace. There is no need to move up they keyboard and to the right and then up the screen to scroll.
Lift your arm up? I can rest my arm on the desk and have my thumb in the lower right corner of the screen. It's actually much nicer than having my hand in front of me slightly raised to have two fingers to scroll with. Try it now.
Yes, but then you just have one hand on the keyboard. So now to type, you have to bring your right hand down, and resume typing. The distance there is greater vs. using the touchpad. I just have to flick my wrist and boom, I am on the touch pad scrolling. On Surface, assuming I hate the touchpad and want to use the screen, I have to take my hand off the keyboard, put it on the screen and start scrolling.
Why do you assume that you have to use the screen or the touchpad exclusively? Surely if you're going to be fliting back and froth between keyboard and scrolling you'll use the touchpad but if you're reading a longer form article you rest your hand on the desk with your thumb on the screen and scroll comfortably. Both can work.
> It is far far faster to scroll through a web page with the touchpad.
This is true if you are the only one using it. If people are standing around you or over your shoulder, and you are all interacting with the screen - then a touchable screen is more quickly usable than shuffling who-has-the-keyboard-mouse. Not saying you are wrong, but there are scenarios where a touch screen is the "best" of the available IO options.
It's a, very natural, quarter inch movement of your thumb while your arm rests comfortably on the table. Not unlike having your hand on your coffee mug.