I find that the biggest benefit to having the levers set higher is that you feel more "in" the bike so that when you get to an almost stalling situation (or the front wheel, at least) you are more able to push the bike ahead of you and through the obstacle rather than ending up hanging over the front wheel - ok, I know that you could still keep your wrists down and run the brake levers low but I usually have a finger hovering over the lever in most situations and so it's far easier if the levers are set that bit higher.
It works the same for me as keeping my heels down on rocky, rooty descents and drop-offs when you want to push the bike off ahead of you.
This is just my take on it however - BITD (late '80s/early'90s) I used to have my levers set really low, along with long stems and stupidly narrow bars. What fools we were.....
But then it was all about racing and times change. I ride much more demanding stuff now than I did twenty years ago.
It reminds me of reading a Sammy Miller motorcycle trials book, - "Clean to the Finish" it was called, where he advocated never
using the clutch to control speed in a section. That advice must have handicapped many young trials riders (myself included) who thought Sammy was akin to God and that his advice was law. We did discover the error of our ways though