The only reason I wear a helmet is because it is required by law in my state. I don't like wearing a helmet for personal safety reasons. I have a bulging disk in my neck and any trauma to that particular place will cause me to be paralyzed from the neck down. If I crash (and, YES!, I have crashed before!), I have a 50/50 chance of hitting that spot on my neck. If I am wearing a DOT approved helmet when I crash, I have a 100% chance of hitting that spot. Every DOT helmet I have ever tried on hits that precise spot on my neck. The slightest bump to one of those helmets while it is on my head and it's bye bye to everything from there down to my toes. Because I am required by law to wear a helmet, I wear a half-helmet that doesn't come all the way down to that spot on my neck.
The way I feel is.. if I want to take a chance on becoming paralyzed, that is my own business. I don't want someone else forcing me to up the odds. I prefer a 50% chance to a 100% chance of paralysis.
On to the rest of the reasons... restricted peripheral vision, subdued hearing, and all the rest of the same reasons that have been hashed out over and over again. The biggest being the removal of the freedom of choice. I am not a child and I don't like being treated like one. Being told to do something "for my own good" irritated the hell out of me when I was 5. At 50, it still irritates the hell out of me.
PK