the proxy stat for what you're looking for, Leo, is the fact that there has been no measurable decline in the number of fatalities even though helmet use has been steadily increasing over the last 10 years - meanwhile skier days remains flat. So we have the same number of participants and the same number of deaths, but twice as many helmets as a decade ago.
I'm not interested in helmet use so I can go beyond my skillset.
I think a lot of people do use a helmet this way and so they take bigger risks. This is well-documented form of moral hazard. Seatbelts and airbags and insurance policies suffer from this, too. Basically when you think you are being protected, you take more risks, which in some cases can negate or mitigate the protection!
And you probably succumb a bit to moral hazard even if you're not chucking yourself off 40-footers. The beginner rider or intermediate is going to feel safer, and as a result subconciously might take more risks than otherwise.