Yes, on a solo MTB ride. I had a lot going on at work and was distracted. I realized I'd forgotten the helmet about 10 minutes into the ride and went back to get it. A ranger was driving by, saw me without the helmet and came over to give me a ticket. I told him that I'd forgotten it and came back to get it. He didn't believe me so I told him to put his hand on the car hood to feel that it was still warm from the engine. Then he started lecturing me about helmet use as I was getting the helmet. I put it on and and left while he was in mid lecture.

Having had a crash that resulted in being unconcious, I'm wearing a helmet. It won't prevent crashing or concussion but its better than no helmet.
Besides its required for racing.