City Riding, helmets or style?

Recently I have been spending some time riding around some cities here in Japan. I am happy to see so many people using bikes these days. It could be the economy or enviromental issues that have gotten more folks riding but it does show that the bicycle is a very good solution for this world.
When I ride in the city my biggest concern is safety, I need to have good vision, good brakes and quick reactions. I almost always ride my Mountainbike, I am sat up on the bike looking at all my surroundings , the disc brakes will stop me quicker than anything else available especially if it is wet, and with the high volume tires I can at least try some sort of manouver if a car happens to attack, and attack they will.
I consider myself a very good cyclist, I have ridden as a courier, a pro-racer and now as a guide and I always ride with a helmet. Why I wonder do all these smart well educated people ride around on their fancy bikes without a helmet on? "I don't want to mess my hair" is the answer I hear most , second is "helmets don't look cool". Whatever the reason it doesn't cut with me, I have crashed many times over the last 20 years, both my fault and sometimes caused by others, 3 helmets have been demolished during this time and each time I broke a helmet I walked away, and each time I crashed were times that I would consider low risk riding, you just never know when you will go down, but you will.
I urge you to wear a helmet ask any doctor they will back me up, you are putting yourselves at an even higher risk than we already are.
Paul