After 2009: at least 80% of adult skiers in Austria and Germany wear helmets, from the looks of things. Most frequent non-wearers are very old, permanently tanned Austrian men who literally have 5000+ ski days behind them or young ladies with nicely-done hair and make-up much more interested in getting good pictures for Instagram than actually skiing.
What happened in 2009? The Ministerpräsident (think US state governor) of Thuringia, Dieter Althaus, was flying down a black (expert) slope, turned onto a blue (beginner) slope with enough momentum behind him to go up it and crash into a lady from Slovakia.
He was in the hospital for weeks, living to earn a criminal judgment for negligent homicide, paying tens of thousands of Euro.
She died on the way to the hospital.
He was wearing a helmet.
She wasn't.
The absolute crush of helmet sales then and continued rates since are sometimes called the "Althaus-Effekt".
https://en.wikipedia.org/wiki/Natasha_Richardson#Injury_and_...
long answer: branding
anecdotally, am a daily skateboarder and long time snowboarder who is guilty of having an ego, and even wear pads to protect a couple massive contusions (swellbos) but i never wear a helmet, so ill frame it like this: 95% of the time i am not that much at risk for serious head injury when skating, and even though i take it for granted, there is an element of knowing how to fall/bail early and skating just within my means.
however on a snowboard, i am much more acutely aware of the consequence -- my casual and super comfort "resting" level is like 25-35+ mph, which is a car accident, which is almost always a threat for serious head injury.
there is a huge difference between tripping at about walking/jogging speed and hitting your head versus at 35mph, and this realization happened after 15 winters of safe riding without a helmet.
the reality is, i am just not that worried about it -- ego or no ego, except when i snowboard, which i will not do without a helmet anymore.
./shrug