[reinout]

Depend on the country, or more likely on the amount of cyclists. In the Netherlands, they consider the 1000kg steel cars to be the real dangerous threat, not the cyclists. It may sound like a play of words, but it isn't. Everyone cycles, so when you hit a junior cylist, you've pretty much potentially hit everyone's kid. People have been known to get a veritable witch hunt on their asses by local newspapers that way.

The car driver gets the blame, not the cyclist that forgot to wear a helmet.

So the key to safe biking is lots of bikes. Sadly, dressing up like for an execution ("I will get hit by a car door and the car owner can just say sorry and move on so I'll wear body armor") won't get society nowhere.

Note that it might very well be an individual's best choice in some countries, probably also in yours... But it is a sad best choice.

[snowwrestler]

It's not about blame, it's about preventable injury. It's about reducing the chance you'll get a call from the hospital saying "your kid has had a bike accident and she is in a coma." I've had friends who work in ERs have to make those calls. In many cases if the kid had been wearing a helmet they would have had a mild concussion. Instead their life as they knew it is over.

If you don't want to wear a helmet, that is of course your decision. I just object--strongly--to your contention that helmets aren't necessary in commuting. That statement is just not based on any measurable facts.