As for your point about cost, I get it. I didn't buy a helmet until this year because each dollar I spend on skiing would probably have a better use elsewhere. I never buy skis over $200; my jacket's ten years old (and leaking); and my boots are used (and not that great-fitting). But I love to ski -- and I value my head, my wife's head, and especially my son's. So as soon as I could justifying getting helmets for the adults, I did. (My son's never skied without one.) But for those people at the mall -- walking is cheap, and so is running, and much more effective than skiing for bringing down the waistline and bringing up cardiovascular capacity. So I'm not sure about the cost argument. Is it a good enough reason to risk brain damage?
Skiing I don't think is much less risk-controllable than, say, driving or motorcycling -- as far as what individual behavior can control. Speeds are lower in skiing. But other skiers are like other drivers, and in skiing as in motorcycling, surface conditions can nail you (a little brake fluid on a curve at seventy -- whoo!). I can drive as cautiously as I like, but, as I said above, some kid could just as well be doing tricks on the roadway ahead. (I had a half-second to react, the cops told me -- not enough time, even when you know what's going to happen.) And motorcycling? Cars DO NOT SEE YOU. Sometimes they change lanes abruptly. It just happens; you have no control.
The parking lot thing makes sense, although I think the variables are generally fewer there, and the speeds involved less, than on the ski slope. Maybe not.
Anyway, I'm still curious about the increase in head injuries attributable to bike helmets. Has anyone analyzed this data?