I got a concussion not wearing a helmet about 12 years ago and have worn a helmet every since. Even if that had not happened to me I would still wear a helmet for three reasons:
1) First and foremost, I have children and need to set a good example for them and not get hurt so that I can be there for them.
2) My wife is a doctor and after working emergency room covering trauma (during her residency) she emphatically will tell anyone who asks that she would NEVER ski/board without a helmet (or ride a motorcycle under any condition). She is not an alarmist at all but has seen first hand the effects of head injuries and the ability to try to protect oneself by putting on a helmet is so easy.
3) No matter how good of a rider you are, stuff happens (that is why they are called accidents). It can be another rider, tree stump or rock you don't see when conditions are poor, etc.. that creates a bad situation.
I don't pass judgement and folks can do what they want but I am surprised that helmets are not mandatory on all mountains and believe they will be.