My only input is that my cousin is a Nurse & has seen icky bike injuries & wont go a foot on a bike without a helmet.
I had a personal experience with my head vs. a low hanging tree branch. It was just a glancing blow, but without my Specialized Max helmet, my gigantic melon would have lost some flesh. Since I have very little hair left on the top of my head & don't enjoy pain I am glad I always wear it riding.