The choice is yours when defining the level of risk you are willing to accept. A USAF pilot who got badly burnt following an overrun in a T-33 made a career of lecturing crews to wear natural fibre clothing as he had suffered badly from synthetic fibre burns. It's the little things that can change your life for ever.
My National Guard Aviation Operation had the fellow give us a presentation about his T-33 crash....and along with the natural fiber emphasis he also stressed other very important issues re safety and survival actions during crashes.
It was a very good presentation as he was very entertaining while discussing a very serious topic....his dry sense of humor was very enjoyable.
Helmets are an excellent asset when it comes to head trauma events.
Many years ago I laid a motorcycle down at highway speed....killed the motorcycle in the process...and only got a few patches or road rash on me...but dented the Helmet on something hard like the concrete curb but no injury to my noggin.
I bought a new helmet as the other was no longer usable due to the "crush" damage to the interior cushioning material.....about two weeks later....I killed a Deer while riding to work before daylight. Again no damage to me despite my having head butted the Deer as the bike and I simultaneously hit the Deer.
Helmets will save your life....period.
Add NVG's and a Battery Pack...and you might encounter a situation where all that added weight could cause a serious or fatal neck/spinal cord injury however.