Uh... aren't those kinda the same thing? Making the game harder and to add challenge?
Edit - Ralos beat me to it...
Yes he did, not fast enough!
Well let me try to explain... Yes they are similar, of course. But to me, it's kinda like this:
Oh God.... I need to find a place to sleep real fast, or my character's gonna pass out, possibly get attacked while I lay somewhere helpless... Darn I have to abandon everything, gotta get to a bed.... vs.
I'm starting to feel pretty exhausted, I better start looking for a safe place to put my head down. (finds a safe area after a little time) Ah, this looks good, set up camp.
Almost like "stressed I'm gonna die if I don't find sleep" vs. "a strategic plan to rest when required"
It adds a bit of realism, and that survival instinct... I guess the challenge is not forgetting to plan your route and actions accordingly, and remember you have to sleep at times, shouldn't be hard with the right strategy, but a challenge nonetheless... Anyway, I see them as 2 different things.