Re:
There are, they just don't bother mentioning it.
Cycling is more dangerous than walking because you are going slight faster. And you do out yourself with killing machines. Same as if you walked on the road, but you tend not to do that.
A helmet will not save you if a truck turned left and crushed you under its wheels, just as it wouldn't if you walked.
Or a truck mounts the pavement and swears blind it didn't see you.
There are limits to everything.
I do know a helmet did stop me getting bruises and headaches after a retrobike national and a posh land rover accident at some speed. (From me, not the car, it had just stopped).
I dented the bonnet and wing with my head and landed on rocky edging /road with the back of my head.
(Other might know better how thing bashed what).
I walked (ish, after a long lay down blocking the road in the moors for some hours and a nice trip to the seaside hospital).
Anyway, the helmet of course cracked front and back.
Did the helmet do any more than what I say, I don't know but I was comfy afterwards and didn't need time off work.
Do I always ride with a helmet, no it's 50:50 when commuting on our roads (I use it more for the visor). They 30mph max but busy.
Off road, nearly always as I use it as branch protection and again the visor for rain and sun shielding.
Do what you want, I do.
I also do know tales of accidents in dalby and simple sections, needing airlifting and not pretty sights.
Would they be any better with a helmet, apparently so, from the people that deal with it and see the accidents with/without helemet in similar situations, the answer is yes they would be better with a helmet.
It's not about brain damage, it's about general protection for a few quid.
As for children, that's up to the parent/career to decide.
Have fun, whatever you decide.