Hmm, this is interesting. I hope it will encourage a few more people to wear a brain bucket ;D I always wear a helmet while riding. The choice is personal, of course, but all of the arguments against wearing one that I have heard were vain, uninformed, or easily dispelled. Things like "They're ugly" (Not as ugly as you'll look in a hospital bed. Besides, there are stylish ones), "they're painful" (then get one that actually fits), and "they're too expensive" (Not as expensive a an ER visit. And yes, you can find helmets that are very affordable, and offer the same amount of protection as the more expensive models). So yeah, they don't have to be a big deal; you can make one an essential part of your riding outfit. They're an equestrian icon, after all.
When I was a stupid kid I never wore a helmet nor had the money to buy one but now that I'm older and more aware I always wear one. My life has definitely been saved by a helmet. And once when I forgot I ended up on a dangerous horse and had concussion for a week. Kids think they're invincible and parents should enforce that their children wear helmets. Adults should be smart enough to know better.
I live by the motto: Every ride, every horse, every time" when it comes to wearing a helmet. It is a lifesaver!