I wore a helmet for 15 years in the military and I am glad had the protection as the flying was -by civil standards - risky. I flew HEMS, SAR and firefighting when I left and also wore a helmet and again was glad because of the inherent risks.
I now fly offshore and am glad that i don't wear a helmet as it has to be one of the safest forms of flying around and helmets are bloody uncomfortable - even a well fitting Alpha. My David Clark headset is a blessing after 6 hours in 40 degree temps.
Wear a helmet if you want by all means but don't make the things mandatory.
Wear one in the sim? Give me a break. Might as well wear one in the car.