Agreed to a certain extent. I hardly see a thousand injured wrists for every head blow on the mountain, but I see your point.
Weigh the consequences of each type of injury. A wrist injury has the potential to ruin your season, a head injury has the potential to ruin your life. I'd rather take my chances with a wrist impact sans guard than a head impact sans helmet. And unless you've taken a blow to the head without a helmet recently, I'd wager you'd make the same choice as me.
And my accident prone wife wears wrist guards (Burton support), in addition to her helmet. I wore wrist guards until I developed the presence of mind to stop throwing my hands out when I fell.