The modern car itself, and several of its safety features, act as a fairly effective "helment".
In San Francisco (and I assume many other places) the parking enforcement cops ride these little things called "interceptors"[0]. They're little more than 3-wheel motorcycles with a body around them. They don't really have much in the way of safety features, so the drivers wear bike helmets.
It's about gauging risk and determining what's likely to help. I would bet that if everyone wore helmets in cars, it wouldn't change injury/fatality stats a meaningful amount, beyond what seatbelts, airbags, etc. already do. But for bicycles (and perhaps these "interceptors", they perhaps do make a difference.
In San Francisco (and I assume many other places) the parking enforcement cops ride these little things called "interceptors"[0]. They're little more than 3-wheel motorcycles with a body around them. They don't really have much in the way of safety features, so the drivers wear bike helmets.
It's about gauging risk and determining what's likely to help. I would bet that if everyone wore helmets in cars, it wouldn't change injury/fatality stats a meaningful amount, beyond what seatbelts, airbags, etc. already do. But for bicycles (and perhaps these "interceptors", they perhaps do make a difference.
[0] https://c8.alamy.com/comp/2GED3CT/san-francisco-usa-april-8-...