Aplogies if people took my Dirty Harry quote as a cheap insult.
Im a pretty competant rider. I know all the usual dangers to avoid and most of the unusual ones. I dont just fall off, and in my 30 years riding I have had 1 self inflicted crash, a couple of scary moments and 1 car-inflicted crash. The worst injury was a grazed knee.
Still, I am aware that sometimes things just go wrong. When several things go wrong together you just got unlucky and are probably going to crash. A helmet may help in some cases to reduce life-changing injuries.

A lot of safety advocates put helmets at the top of the cycling agenda. I put them at the bottom, quite literarally your last resort after everything else hs failed to protect you.