Paul,
The biggest single risk to skiers now are the !#@$#^%$#%@% snow boarders. I have a friend who got a shattered ankle from being hit from behind by one. Every week I see people get run into by these jerks. PSIA is well aware that there is a significant risk of serious injury at low speed; low speed twisting falls are the worst, well maybe not as bad as hitting a tree at 40mph. People who ski very slowly and cautiously are not doing themselves any favors. But, those people usually are not confident in their ability and after watching a fair number of them, they have good reason not to be confident. PSIA is starting to pay attention to the baby-boomers and a couple of regions already have special instructor training for teaching seniors. But if you're 60+ and some 20-something instructor tells you you can do something, how inclined are you to accept? If a 60+ year old instructor is saying the same thing, they're more likely to listen.