I've been cycling almost daily for all of my life and only once had an accident where I hit my head, back when I was 6.
Disclaimer: I live in the Netherlands, bikes are everywhere.
The main difference is that here, you have experienced cyclists (you learn to walk, then you learn to ride a bicycle), dedicated bicycle lanes, and car drivers that know there's cyclists around and look out for them.
As for helmets or not, it's very much a factor of speed, risk of accidents, and the nature of the accident. Hit your head at a high enough speed (iirc, anywhere above 30 KM/h) and you'll get a concussion, even with a helmet. Maybe no cranial fracture, but still. Helmet won't protect you from breaking your neck or getting run over by a semi either.
tl;dr, I don't wear a helmet, I don't need to, and I live in a country where cyclists are common. You do see people wearing helmets, but they're usually children in busy cities or speed cyclists. Sometimes both.
It's true, one very rarely meets people who have suffered serious head injuries without a helmet. You will never talk to a cyclist with that kind of serious story.
It's a sampling problem: you only talk to cyclists. The head-injury cases who didn't wear helmets are injured or dead, and correspondingly no longer cyclists.
If you lived in NYC you would wear a helmet. Or should. And I would say NYC has more experienced cyclists than the Netherlands, considering what New Yorkers have to put up with. The dangers of NYC cycling is the density of things that can hurt you moving around you.
NYC has a population 10.40 times larger than the largest city in Netherlands (Amsterdam), with a density that is 7.85 times greater.
FWIW, I had two bike crashes in the span of one week where I hit my head. They were both in races though. However, I was going more than 30km/h, and I got zero concussions. I am glad I was wearing them.
Disclaimer: I live in the Netherlands, bikes are everywhere.
The main difference is that here, you have experienced cyclists (you learn to walk, then you learn to ride a bicycle), dedicated bicycle lanes, and car drivers that know there's cyclists around and look out for them.
As for helmets or not, it's very much a factor of speed, risk of accidents, and the nature of the accident. Hit your head at a high enough speed (iirc, anywhere above 30 KM/h) and you'll get a concussion, even with a helmet. Maybe no cranial fracture, but still. Helmet won't protect you from breaking your neck or getting run over by a semi either.
tl;dr, I don't wear a helmet, I don't need to, and I live in a country where cyclists are common. You do see people wearing helmets, but they're usually children in busy cities or speed cyclists. Sometimes both.