Re: A Cops perspective....
After you get into the habit of wearing a helmet you'll feel naked without it. But I'm basing this opinion on MC riding. At speeds above 30mph, you'll be faster than the insects and you'll be eating bugs. And when a bug hits your face at 40mph it can sting pretty good. I've taken my open face motocross helmet (use goggles too) off several times and have found bee carcasses stuck in the liner. And I've been bee stung several times also.
However, I do understand the riders who stay under 30mph not wanting to wear one. And I don't have an opinion either way. I believe in freedom of choice.