People do still receive head injuries from car collisions even with airbags and seatbelts, so it's reasonable to think that wearing a car helmet would provide additional head protection - it's certainly common in motorsport.

I'm trying to compare activities that have a significant risk of head injuries (and deaths) with cycling and yet PPE is very rarely mentioned for them.

Motorsport doesn't use airbags and has a steel tubular cage exposed directly to the occupants, the helmet is mostly for protecting from impact with the cage AIUI.

All those grease monkeys driving around with aftermarket cages in their cars and not wearing helmets are actually less safe for it. The last drag strip I was at wouldn't even let you run if you had a cage and no helmet to accompany it.

Airbags and no steel tubes next to your head change the calculus completely.

I mean, basically any adventurous activity where you're moving [quickly] with equipment gives rise to use of helmets - kayaking, rock climbing, roller blading, skateboarding, skiing, skydiving, horse riding, ...

Can I ask, is it only safety equipment for cycling you're against?

It looks like you're trying to argue that people shouldn't wear helmets when cycling because people in cars; that have protection from a steel cage with crumple zones, and airbags, and seatbelts, and cushioned seats; don't wear helmets.

Like, sit in your car and get someone to launch a paving slab towards you; then sit on your push bike and do the same thing ... I'd do the first without a helmet, I definitely wouldn't do the second without a helmet (or at all). I can't see how you can find these situations comparable wrt indication of benefit from a protective helmet.

I'm not "against" cycle helmets, but think that their benefits are over-sold. The big issue is when people think that bike helmets are an important safety aspect of cycling, when they're probably not even in the top ten. It's interesting to see different countries' attitudes towards road safety and cycle helmets.

For the record, I always wear a bike helmet here in the UK, but I am not convinced that they really provide much benefit. There's plenty of different studies on bike helmets and a lot of them are very flawed (quite often ones that are sponsored by helmet manufacturers), which is worrying as it should be easy to demonstrate if they are having a big effect on road safety. My opinion is that population wide, they do provide a small benefit, but they can also act as a barrier to cycling for some people, so it's best to not over-emphasise them.

The health benefits from active travel are undeniable, so I'd prefer cycling to be promoted as much as possible and talking about helmets is missing the point.

Perhaps those activities _should_ be discussing helmets.

Most sports where participants could materially benefit from helmet use absolutely do discuss helmets though usage varies from common (e.g. recreational downhill skiing) to almost universal--whitewater kayaking.

Downhill skiing in particular has transition from essential no non-racers wearing a helmet to quite a high percentage in maybe a couple of decades.

In 2009, a German state governor caused a terrible skiing accident, which he survived but the victim didn't. He was wearing a helmet, she wasn't, and after that point, helmet sales in Germany and Austria shot through the roof and use has remained high. Before that, it was pretty much only racers and children.

Natasha Richardson (reasonably well-known actress) also died the same year from a skiing-related brain bleed. And yeah, while I haven't had a lot of visibility into ski area helmet usage over the past decade, that does seem to be around the time when it really shot up.