I bought my first (only) helmet circa 1996 to set an example to our children. It is very dated now. Probably also useless after many drops onto stone floors.
I wore it rarely until about a year ago when I got caught in AWFUL weather.
Roads like sheet ice and holes hidden in every puddle. Close passes aplenty and abject terror.
I simply got scared and was beset by supestition. Out went the casquette I'd always worn.
Now I wear a helmet often. I really wish I didn't, but I've become superstitious and scared in middle age.
(I've only crashed twice since this change of heart, both times sans casque.)
When I wear it I miss being able to scratch my noggin.
Weirdly, I almost always get terrible road rash when I crash, but I still wear lycra with no armour or padding.
TdF looked better before helmets, but I just feel safer sometimes with a helmet on. Not always, but sometimes.
I'd prefer my children to wear one, but I am not their master. 1 does always. 2 do sometimes...