I can understand the OP's thinking, although I have Lenovo's Yoga 2 Pro.

With my laptop in my lap, I typically have to be leaning back to comfortably use the keyboard. Sitting up or slightly leaning forward, it's more comfortable to grasp and scroll with the screen itself, maybe bent a little further back than typical usage. It's a more comfortable resting position.

Although sometimes I just flip my yoga into a tablet and that's just swell

Many times touch is more convenient than the trackpad especially when I am feeling lazy. I am reading this thread on a Y2P, lying on my side, laptop on the bed, one hand supporting my head and the other scrolling the page on the screen. Much easier than any other method.

when in tight vehicles (or even lying on a bed/couch), the spacebar is highly inconvenient (and often requires changing your grip of the laptop). I have used pg up and pg dn on laptop keyboards that put them in their proper place (top right by hinge). I agree with parent that touch screen is particularly nice for this (and I also never thought I'd appreciate it)

Spacebar/pgdwn is a harsh context break for me. There's no continuity like a book or touch screen

> harsh context break for me. There's no continuity like a book

more than a page turn?

I find the continual swiping distracting. And it's a much more complex motion (akin to a page turn) and must be done more frequently than paing. A tap of the space bar is about the simplest motion, and (except in cases of bad page design) gives a clean "start at top for next page" rather than trying to figure out where on the screen your next line is.

Preferences vary, obviously.

> more than a page turn?

Yes, a page turn with a book gives you a very specific place to continue. Spacebar or page down doesn't.