When I was 8, had a friend at school, his older brother was riding his bike, got hit by a van, wasn’t wearing a helmet.
Kid became a vegetable at 10.
That sort of shit sticks with you for a long time. Always worn a helmet since. Under all circumstances.
You know that a bike helmet is zero protection against being hit by a van, right?
Please don't get me wrong. I think wearing a bike helmet is a good idea and (as they're both cheap as well as relatively inconvenient to wear) everyone
should wear one . . . but many people have a bizarre idea of what a bike helmet is meant to do. It's designed to protect your head if you come to a stop on your bike, lean over too far, and smash your head on the curb. The primary test that is done on bike helmets is dropping them 2 meters. That's it.
If you're hit a slippery patch on the road and wipe out at speed, it isn't going to do much for you. If a vehicle hits you, it isn't going to do much for you. If you panic brake too hard while moving fast and go over the bars, it isn't going to do much for you. Sure, everyone should wear one because it will probably help
a bit. But it's not going to work miracles. Expecting a helmet to miraculously cure being hit by a van is crazy . . . and it's distressing how often terrible injuries caused by collisions with vehicles get shrugged off by 'well, he wasn't wearing a helmet'. As if that makes the outcome of the accident the fault of the cyclist somehow.
Cycling, especially cycling at low speeds (as children do) is a very safe activity. Your risks of catastrophic head injury is extremely low unless a vehicle is involved. The best thing to do if you're concerned about collisions with vehicles is to convince more people to ride bikes (even without helmets). Multiple studies have proven that accidents, injuries, and fatalities go way down when drivers become more used to regularly seeing cyclists on the road.
That's my mini-rant anyway.