I've almost always worn a helmet. Mainly early on, I got one because I had to participating in an organized bike ride. So having one, I wore it most times.
Few years later I went out for a ride thinking I would leave the helmet at home so that it would force me to go easy on a mountain bike ride. I had done a tough ride and wanted to ride just to relax the legs. The loop was 5 miles on hard packed red clay in one section. 15% grades so getting some speed on the way down.
This is the profile but only one loop that day. 1,000 ft gain in a couple miles so one comes flying down. I planned to nurse it on the way down not having a helmet
But I at the last second decided to take my helmet, good move!
I had actually gone as easy as possible and crawled on the descent. But the last 1/8 of a mile, thought I was clear so I let the brakes go and got up to 25 MPH.
****! It was a couple days after a rain and when I hit top speed, I saw a big wide huge rut that had formed. I had no choice but to try the bunny hop, nope! I hit the opposite side of the rut with my front wheel. I remember going over the bars then everything was blank. I ended up on my back hearing my bike tumble down the road.
Strange because there was no pain so I thought I was dead not being able to move for 30 seconds or so. Amazing at the human body's self defense mechanisms.
So I got up and noticed my helmet was pretty well cracked in the back. This is one of 3 pics that show the damage (somehow lost 2 somewhere along the line) . This was not all, there were scrapes along the back of the top as well.
I counted my lucky stars that I was wise enough to decide on the helmet that day. It is those days when you think nothing will happen, that they happen!
Since then, I have always worn a helmet. I think of that day and if I had ended up in the hospital with those breaks in my head rather than the helmet, how stupid I would have felt for not taking the helmet.
So I don't care whether anybody else does or doesn't wear a helmet. I care about my head!