We didn't have bicycle helmets when I was growing up, and most kids survived without them. And because of that, many people have the attitude that if it was good enough for me, it's good enough for my kids.
However, my kids did grow up in a time with bike helmets, and I made them wear them for a few reasons. First, it was recommended by the American Academy of Pediatrics, and secondly, they were required by law. Both were based on safety concerns for head injuries. On top of those, my sister worked at the John's Hopkins trauma center, where patients would come from around the country for an evaluation and treatment plan. She was on a team that helped do that. My sister saw many bad head injuries from bicycle accidents where the rider was not wearing a helmet, and she begged me to make sure that my kids wore them. So if I had been on the fence before, she definitely convinced me of their importance.
I was having this discussion with one of the other mothers in the neighborhood one day, and she told the story of how her daughter had a bike accident, and the helmet saved her life. In fact, the local police used her helmet when they would give safety talks to drive home the point of their importance. But here's the part I didn't understand. Her daughter rode her bike all the time without her helmet, and her mother didn't bat an eye.
That wasn't me. So were my kids the weird ones because I made them wear a helmet? Did they protest? Yes, but sometimes you have to be the grown-up and do what you think is right.