I strongly disagree, at least for a place with good cycling infrastructure like the Netherlands.
We lose the helmet at age 8 or sooner. Pretty much as soon as you can go without training wheels without being scared of losing your balance, you don’t really need a helmet anymore. Learning how to fall off your bike without serious injury (at normal speeds) is an important skill that you should know by that point. I’ve fallen off my bike probably more than 10 times throughout my life (mostly due to ice) and I’ve never had worse than a few scrapes and a slightly tender bone in one of my fingers.
Cycling is much safer than ice skating and people skate without helmets all the time too.
The risk of injury because of a careless driver along major cycling routes is very low, since our roads are built to give people leeway and reaction time at intersections and drivers are used to being careful with cyclists.
The only times I’ve felt afraid of motorized traffic while cycling to school were either because I crossed the road with a bit too cocky timing (on a road where cars don’t go faster than 30kmph anyways) or because occassionally some drivers were going over the speed limit and passing me closer than usual on a rural road that didn’t have the cycling infrastructure that most places in the Netherlands do have, with that rural road also being in a “silence zone” where cars aren’t supposed to go if their destination is not along that road. (Happened 2 or 3 times in 7 years of daily 45min commutes to school.)
Still, I haven’t once been in an accident with motorized traffic, and I don’t know anyone who has either.
The only head injury among people that I know was one (at the time) 10 year old kid who was looking at his phone while cycling and fell onto the towbar of a parked trailer. He had 7 stitches and a light concussion and ended up with a thin vertical scar on his forehead. (IIRC, it was over 10 years ago)