I won't try to convince anyone one way or the other - just simply elate some of my experiences:
When helmets first came out I wore them - I had the old Gyro foam helmet, and an old Belkin "Bucket", that I wore when I did my first double century in Davis, Ca. Years later, after moving to Arizona, I decided to sacrifice safety for comfort - I sweat like a horse and I hated to have seat pouring down my face while wearing a helmet. Besides, when I crashed I always managed to prevent hitting my head.
Then one day, I wore a Gyro foam helmet while screaming down South Mountain from the TV towers; I lost control in a turn and crashed - I hit my head so hard on the pavement that I saw stars! My helmet was split but I suffered no head injury. I changed my habit. For awhile.
Fast forward a few years and I'm commuting to/from work at Boeing in Mesa to my home in Fountain Hills. A teenage girl driving a car pulls out in front of me and we collide, trashing my front wheel and bending my fork. No helmet. But no injury. Lucky. My wife insists on my wearing a helmet - no excuses, no exceptions - Period.
I am now 62 years old. I still ride, still wear helmet. But my main ride is a recumbent trike. Do recumbent drivers need a helmet? One can argue pro and con. For me, I wear one. I have a Gyro Air Attack because I like the visor. When you ride a trike in the morning you tend to fin yourself looking into the sun. I like the aero characteristics, not to mention the "jet pilot" look. And it serves as a mount for a video cam, which I like to use on some rides.
So there it is - I have no regrets and a helmet has saved me a couple of times. Just one save is worth the cost of all the helmets I've purchased.