I never used to wear a helmet. Year and a half ago I worked for a Major resort in the ski industry here in Colorado. I worked with ski patrol (not for) and with the ambulance, assisting in patient transfers. Seeing some of the people come off the mountain will give you another perspective.
1. I saw a 14 year old kid come off the mountain, he was violent, crying, lost, not there all at once. He hit his head snowboarding. Long long story short, I saw him two years after his accident and he was not the same. I had talked with his mother several times and she had said they have spent a lot of money trying to make him right again, and she had accepted that he wouldn't be right in the head ever again. This kid had his entire life ahead of him and will probably never be a productive member of society because of his crash and head injury. All because he didn't have a $60+ helmet on.
This was just one example. I saw lots of adults, lots of kids come off the mountain with head injuries. You say you just do groomers but all it takes is one other say 14 year old kid flying down the mountain out of control to collide with you. Your decision to not wear a helmet could mean your family doesn't have one of their bread earners supporting them. Honestly, it's just stupid not to wear a helmet. You buy insurance for your car, have health insurance and probably wear your seatbelt. Do you really plan on crashing your car? You have it there for that "what if" scenario.
Most major ski areas require all staff to wear helmets. I honestly don't think it will be long until they require anyone on the mountain to wear a helmet. Most require a helmet for any ski lesson already.