Yeah, I have no idea why they removed them. The swipe combined with the high response time means I never know if it registered the swipe and always go back and forth in an effort to change pages.
They probably saved some trivial amount of money on manufacturing costs by removing physical switches, seeing as how they were implementing touchscreens anyway for the rest of their interface.
Smartphones initially had physical buttons that have gone by the wayside now, but at least their screens are much more responsive!
I really wouldn't mind having physical next/prev page buttons, though. Having to touch or swipe the screen is kind of annoying. I feel like that's a step back in UI from previous gen devices.