For adult helmet use:
This is a discussion of risk. Risk to ones self and risk to others. The risk to others is the financial risk of supporting the injured person through disability assistance or increase insurance rates, etc.
All things have some level of risk and we, as a society, accept different levels based on, in part, these three factors:
1. How high is the risk actually.
2. How high is the perceived risk.
3. How politically correct is it to demand or legislate a change in behavior.
So, for example, it's OK to say smoking is bad and outlaw it because,
1. It has a high actual risk
2. It has a high perceived risk
3. It's politically acceptable to legislate against it.
On the other hand it is not OK to say obesity is bad. because,
1. It has a high actual risk
2. It has a high perceived risk
3. It's NOT politically OK to persecute those involved.
So for helmets...
1. High actual risk?
Don't know. Can someone point to a study? Can we compare the risk to say, a carnival ride, or swimming in the ocean without a life jacket?
2. High perceived risk?
Clearly some think its highly risky. Other don't.
3. Politically OK to persecute?
More and more so, especially depending on the are of the country you're in.
When I was a kid, no one wore a helmet while biking or skiing. Now it's the law for kids under 16 on bikes to wear a helmet, and it's rare to see someone skiing or snowboarding without one.
So we should see a drastic drop in the price of heath care soon right?