If by motorists you mean people in cars they do mandate head protection in the form of air bags and a myriad of other safety features

Sure, but the question remains whether mandatory helmets would prevent a significant number of car injuries and deaths (I'd say that's quite plausible). Whether cars have other safety features already is neither here nor there.

A helmet in a car would limit visibility and movement and is completely impractical, not to mention mildly pointless.

On a bike you are exposed. In a car, you are not. On a bike you travel around 30km average. In a car, up to 100km average.

I think you will find the average cycling speed is a lot slower than that, especially around urban areas where most of the risks are.

See the cyclists in London or any big city blasting though a red light and you would change your mind

Ugh ...

Helmets go on top of your head, they shouldn't limit visibility. The practicality, and point, would be protecting you in the event of a collision.

When travelling at 100km with no seatbelt (legal in many areas), in a collision, you become exposed rather suddenly.

And wear seatbelts, by the same standard.

Don't forget about pedestrians. Helmets are like avoiding ECC RAM, soon you are giving them out on every level of abstraction because you don't want to face the fact that the danger comes from cars/memory with bit errors.

Fix the problem, styrofoam will not save you.

Peds don't share roads like bikes. When I'm cruising on my road bike I'm literally feet away from cars while traveling at a decent clip like 15mph.

Pedestrians are on a sidewalk often with parked cars between them and the threat of tons of steel at velocity.

Scooters or anything going 15mph should not be on a sidewalk.

That's novel of you to try to solve this problem by "thinking", the true sign of a great programmer. Yet here we are and the statistics show plenty of head injuries for pedestrians, and the folly of your thought naturally.

Is there a word for this? Theorizesplaining?

That's what the metal chasse is for. Not to mention airbags. Cyclists don't have those.

No, I mean that many motorist lives would be saved if they all literally wore helmets. They should be required to. Airbags and roll cages help, but they are (obviously) insufficient on their own to prevent the 20k car deaths every year.

It would also help reduce the 200,000+ TBIs (traumatic brain injury) caused by car accidentals in the US every year.

I might be convinced to personally start wearing a helmet if an awareness campaign gained traction. As it is, I will take the additional risk to avoid looking dumb.

I personally believe that (personal adult) helmet laws are a violation of individual liberties but we should create laws that force bike/scooter sharing companies to make sanitary helmets available. It is better to regulate business behavior than personal behavior.

Helmets are also insufficient on bikes but they significantly reduce injuries. With cars I'm not quite sure what problem you would be trying to solve because they probably wouldn't actually appreciably reduce injuries (I don't many of those car deaths are just really simple trauma to the top of the head that a helmet would actually protect against)

Oh come now, top of the head? Full face helmets are the better option, and if we're really looking to be safe, we should require them, and anti-whiplash headrest connections, as well.

Similarly six-point restraints, I'm always confused why there's just a lap-and-shoulder belt in most cars.