Why do People Tell Other People to Wear Helmets?

It is fascinating to see grown adults tell a complete stranger to wear a helmet whilst riding a bicycle.  Why do adults feel the need to tell other adults to wear a helmet when bicycling?  Is it possibly
because the person telling the other to wear a helmet does not trust themselves to look wear they are going when operating heavy machinery on the roadway?  Maybe knowing that someone else is wearing a helmet makes the person driving the motor vehicle feel safer to do things like drive while distracted, drive intoxicated, speed, not look where they are going, roll stop signs and otherwise fail to pay attention to the task of driving?

Think about it, usually when someone yells out, "where's your helmet," it involves a person sharing the road with motor vehicles.  You don't hear people yelling it out at skate parks, trampoline parks, inflatable parks, roller rinks, boxing matches, rugby games, off road mountain bike trails, or most importantly, to other drivers of motor vehicles.  In 2013, 383,231 people who operated motor vehicles suffered traumatic brain injuries in the U.S.  Over the road truck driving is consistently rated as one of the most deadly jobs in America.  No one asks drivers of motor vehicles where their helmet is despite the risk of a traumatic brain injury whilst driving a car being much greater than when riding a bicycle due to things like moving at 70 mph. Concussions occur in one out of every 61 tow away crashes.      Seat belts don't always prevent brain injuries.  Traumatic brain injury is similar among properly restrained and improperly restrained infants in higher speed mvcs

Where else in life do you see adults telling other adults (whom they have never met) how to stay safe and healthy?  Have you ever been grocery shopping and a stranger comes up and says, whoa, you really shouldn't purchase that alcohol or cigarettes because it is harmful to your health?  Or maybe, hey stranger, I see you bought a box of doughnuts and you are already overweight, "where's your broccoli."  Why do people feel more strongly about a stranger riding a bicycle without a helmet than they do about a stranger inhaling an extremely addictive cigarette which increases chance of dying from lung cancer by 30 times.

Is it o.k. to tell adult strangers what to do or what not to do?  Where do we draw the line?  Should we tell strangers not to get the supersize?  To stay out of the ice cream aisle?  To stay out of the tavern?  To not walk on icy roads?  To drive under the speed limit unless perfect conditions? To always use condoms?  How about, "hey buddy, where's your radon mitigation system?" Will the strangers listen?

What about the number one group of people who could benefit from wearing a helmet, the elderly?  When we see a person aged 70 or over should we yell, "Where's your helmet."  Falls in the elderly age category are number one cause of TBI.

Studies have found that obese passengers are more likely to suffer a more severe head trauma after a frontal collision in a motor vehicle.  Should we all start going around and yelling at adult strangers, "Hey, lose some weight, it could save your life?"