It all boils down to risk assessment and subjective feel of "safety".
If humans could live for 10,000 years, then even cycing itself would be an unnacceptably risky sport, since you are most likely to get killed, or become an invalid within your first 5,000 years of cycling.

However, that is not the case. So, while cycling itself has its risks, just like cycling without a helmet does, I'm all for helmets not being obligatory. However stupid it may sound, I've trained judo as a small kid and it's helped me never hit my head, or break any bone, after decades of football, cycling and motorcycling. And I do fall down A LOT. Really. Been hit by cars too - never hit my head.

On the other hand, I've seen people fall down on flat pavement, while on foot, and hit their head real bad. For them it would be wise to wear a helmet when walking.

I wear a helmet on group rides, since I assume there's a lot more chance of things going wrong (10 tightly packed cyclists, if either of them in front of you goes down, you are likely to go down too, in a pile of other cyclists, hitting you and potentially preventing tuck and roll body movement). When riding solo - almost never. Don't like it and consider the extra risk too small to warrant it - just like I don't wear a helmet when walking.

I also teach my kid to think ahead, access risks and take responsibility for their actions and choices.