Gotta remember though, with all the practice and experience, people occasionally do reach out when they fall, it's a natural reaction, heck I never had a wrist injury in 15 years of riding but 2 seasons ago reached out like a moron and broke my wrist (was somewhat alcohol related). All it takes is that one time and you're broken. It seems like my friends and myself usually get injuries in the smaller wrecks, you know just freak accidents. Maybe it's the time in the air gives your brain a chance to go "wait, dont do that!", but I agree with NWBoarder28 that the beginners or people just learning a trick are more concerned with crashing and getting hurt and they react by stopping themselves with any means possible.
I do find it a bit funny that you go to a sled hill and see kids hauling balls, hitting jumps down the hill on sleds with no fear but you put them on a snowboard and they are nervous. Either way, the cool thing to do if you see someone reaching out when crashing is give them a quick heads up on what they are doing so hopefully they don't get hurt.
Personally, I have always tried to take it to the shoulder if possible.