Technically you are correct that wearing a helmet does reduce risk of head injury somewhat. However -when infrastructure for cycling is already very safe- you start seeing all sorts of strange statistical effects; and it is not immediately obvious that helmets are a net benefit.
I looked around a bit to see if I could find a paper that takes a balanced view. This particular paper seems to be a bit more from your perspective where wearing helmets might be of some utility. However it does leave the impression that it is would actually be somewhat hard to break even on wearing helmets in the Netherlands. https://bmcpublichealth.biomedcentral.com/articles/10.1186/s...
The first document explains that people who take risks (like riding at high speeds or on a mountain bike) DO wear helmets in the Netherlands. Which is the reason why helmet wearers show up in hospital more often.
The second is a recent paper that applies evenly to people who ride a bike "normally", [From experience: at low speeds on segregated infrastructure at around 15 km/h or so]. My interpretation is that it concludes that wearing a helmet would improve safety for cyclists somewhat; however it would not (currently) be risk-cost-effective according to their measure; and would require intervention to break even.
There's a couple takeaways from the first article. The cyclists with helmets are the serious ones riding for sport. I'd also guess commuters who are going long distances wear helmets. These cyclists are putting in far more miles than unhelmeted cyclists. I see the same thing in my city; very casual bikers don't wear helmets. Commuters and sport cyclists do. And those groups are putting in the most miles by far.
If zero people rode bikes without helmets, you'd see 0 cyclists without helmets in the hospital. All those injured will be wearing helmets. It's a terrible measure.
You've got the gist of it. I'm trying to point out how .nl statistics come out funny because the infrastructure has been made so safe.
Commuters actually make up the majority of cyclists in the Netherlands, there are a lot of them (cycle commuting is heavily encouraged for all kinds of people at all ages), and they don't wear helmets. Despite the large number of commuters on bicycles, commuting is (apparently) so safe that the commuters are heavily outnumbered by the sports cyclists in the hospital statistics.
It is still a somewhat misleading measure of course. You probably should not conclude that wearing a helmet is highly unsafe. ;-)
And... that's the point I'm making. Take measures from the Netherlands with a few grains of salt, because the situation is atypical. On the one hand it's really cool that it's atypical, but then you do need to watch out. The numbers don't line up with the intuition of someone from a typical cars-are-more-important-than-safety country at all; so it's easy to make funny assumptions and draw wrong conclusions.
What I see in those videos looks just like my university, a bunch of people on what we call beach cruisers going a very short distance. Their speed indicates they aren't going far and aren't in much of a rush. Are people in the Netherlands strict about arrival times? Do they usually move at a slower pace?
In my city commuters go fast. We're going a few miles on a commute at least.
They're going quite a few miles on bike alone. 30-60 min commutes are not uncommon. Kids, Adults, Seniors. Hot or cold, rain or shine.
The time culture is similar to Germany: you have to be punctual. This means you need to leave on time in order to arrive on time. As a general rule in real-world traffic: Speeding might not actually help you arrive all that much quicker, you just feel like you do. An objective instrument (such as a GPS) may well inform you otherwise.
Also, on a bike: if you're traveling longer distances, you need to pace yourself, lest you run out of steam half-way.
The infrastructure is good though, in municipal zones the cycle distance (and time!) can often be shorter than the car-distance; because bikes can take more short-cuts and are easier to park. And for longer distances it's possible to eg. park your bike at a station and continue by bus or train.
Yeah, my dad almost died like that. On a separated bike path in very good condition, he would have only been going about 30 km/h given where it was (he can't actually remember what happened due to TBI but managed to make a full recovery after four months of hospital and rehab). Comparing the size of the foam on the impact side of the helmet vs. the other side was amazing, it was squashed to a fraction of the size. If that had been skull straight onto the concrete it would have been lights out pretty much instantly.
This viewpoint (that helmet wearers take bigger risks) only holds validity when helmet wearing is a choice.
In my country (Australia), helmet wearing is mandatory and the vast, vast majority seem to follow this rule. I've never felt "more protected" wearing a helmet, as I wouldn't ride without one. It's a default state.
AFAIK, in the Netherlands helmets are considered to slightly reduce safety in the general case (but this is not a strong effect).
The general objective is to make infrastructure sufficiently safe so that helmets become redundant.