There is a prominant Sydney neurosurgeon who indeed wears a helmet for driving in his and others cars, guess he's seen more than enough brain trauma in his work day.
And the majority of Qld dermatologists are Vitamin D deficient and some people cannot leave home without checking they locked the door 10 times.
Car safety mods often benefit everyone as much as the driver. Crumple zones, ABS, stability control, etc save other people too. Comparing a car to a bike is not reasonable. Comparing a motorcycle to a bike is also unreasonable as is comparing the helmets used.
Cycling helmets provide limited protection from less serious injury. I am not aware of any convincing evidence they prevent serious injury and there is no evidence they protect the public from cyclists. Children are different. Less mature skeletons and brains cannot be compared to adults. Having said that, a helmet is going to do nothing for a child hit by a passing car as they ride out of their own driveway.
The more cyclists and the more legal support for cyclists in accidents, the better for cyclists' safety. In Holland, a driver involved in a vehicle/cyclist incident is at fault unless proven otherwise. I've posted this on RB before and been told it is wrong and promotes cyclists being stupid. No, it promotes drivers being attentive and it promotes a pro-cycling attitude.
Someone said that people only travel short distances in Europe. I am trying to understand how everyone is that lucky in many cities as large or larger than Sydney. It costs about 50% more per litre of petrol in Paris. If you use 2l (say 20km with a small car) per day, then you spend about $8 more per week than here. 2 coffees per week is hardly a reason to ditch the car. Truth is Australia is car-centric, lacking alternatives acceptable to the public and it is not about cost.
I've read many stories of heads saved by helmets and personally found plenty of scratches and minor dings on my own helmets - bike, moto and road motorcycles. However, I have ended up in hospital and off work for many months after an accident that happened on a cycle path when I was riding at less than 15kph with my toddler on a baby seat behind me. We were cleaned up by a high speed cyclist coming the other direction and hidden by trees overgrowing the path in a place with no escape. There you go, multiple fractures and brain injury and not a mark on the helmet. Kid was OK, but covered in mossie bites after I managed tho crawl onto the nearby road and attract attention some 20 min later. The other rider was still unconscious. He also had a helmet. Kid did say he hit his head, but I guess the helmet helped there and as I have said, all kids should use them.
Personal experience is a reason for personal choices. Regulation for the sake of it makes no sense and in fact creates rebellion and avoidance. Cycling needs public support and that means increasing uptake. On this forum we want to wear our helmets, but that does not speak for everyone. Last weekend I caught up to 4 young guys riding and looking for downhill trails. Never been to the area and had no real idea where they were. 2 had helmets, 2 did not. It's hard to know what to say, recommend or do when you know you are helping people taking risks, but I showed them the way out of the park (I think getting lost was the biggest risk) and gave detailed instructions regarding the trail down and how to be safe on it. They were having a ball and to be honest, that stands for a lot more than being under the thumb of "the man".