In March of '99, I bought my first new motorcycle, a Kawasaki Concours. I rode it home to Ft Morgan, about 80 miles, and the next day I had a meeting in south Denver, another meeting in Cheyenne, and then was going to Ft Collins so Joanne (then my fiancee) before returning home. The only helmet I had was an old Bell that a church member had given me. If the faceshield was closed, it fogged up almost instantly. As I rode into downtown Denver, saw a rock just before it hit me in the right lens of my glasses. The lens popped out and gave me a small cut and a larger bruise. I couldn't see out of my right eye with the correction provided by that lens, so I rode on to my meeting with one eye closed. I called my church from my meeting and a co-worker was able to go by my house and find my previous set of glasses, which had a slightly different prescription, and bring them to me before I had to leave for Cheyenne. The next day, I went back to Denver for the first maintenance check and Joanne met me there so we could both buy helmets. I've only been hit by one other rock (on my way between Haines Junction and Tok, AK), but I've been hit by hail and insects that were big enough to have taken out an eye. I'm always going to be wearing a helmet!
I've worn modular helmets since about 2004 and sometimes ride with them open, while drinking or eating. But in traffic or twisties, they stay down and locked.