There's a flipside in another sport.
In Men's Lacrosse at the college level they wear helmets... in Women's Lacrosse helmets are not allowed, they wear ridiculous eye-cages instead.
Their argument is that they have less contact allowed and don't need them. I think the real thing is trying to look better and/or culture like hockey.
Women's college Lacrosse apparently is #2 for concussions after Men's Football.
Men's Lacrosse apparently has far fewer concussions even though it allows contact.
My wife had 3-4 concussions playing Lacrosse in College.. I definitely worry about some effect of it coming back as we age. Her concussions were apparently bad enough the effects lasted and messed up her schoolwork for quite some time.
I played a lot of pond hockey as a kid.. we somehow managed to not knock each other's teeth out or get head injuries without helmets but there was no contact and the level of play was very low.
First time I suited up in a rink with a helmet I got hit in the head by the puck coming around the boards. I was totally fine cause of the helmet but it scared the crap out of me, I don't think I ever really played pond hockey again.