Is there a lore reason for why we can fall from great heights?

[Akisohida]

It's explained in the same book of why our character never once takes a dump.

Or sleeps.
Or bathes.
Or eats for any reason other than 'stat buffs'. (I can't imagine every person in the world gets a stat buff when they eat).

Though I usually assume those are done when we're offline. At the very least, the 'sleeping' one is; as per the rested bonus. So maybe they take a crap, bathe, eat and sleep when we log out.