This isn't an entirely invalid point people. Yes, our sport will always be dangerous, and there will always be the few people who suffer life altering injuries to the brain (helmet or not), spine, and other less tragic but still serious injuries such as knee issues. However, IMO, the key issue with helmets and brain injuries  is threefold.
First of all brain injuries are in a league entirely of their own when it comes to severity. Now, of course this point is highly opinionated, but I would say that losing your cognitive abilities is probably far more devastating than paralysis or any other injury, mostly to your family/friends who has to deal with the reality that their loved one is a vegetable. At least if you are paralyzed, your mind is still there.
Secondly, in light of the first point, also unlike other injuries, it is VERY easy to dramatically lower your risk of life altering injury, simply by putting a pretty benign piece of foam on your skull. Some might say that, if we are all for protection and safety, why not put on full body armor? The difference is that helmets aren't limiting your movement, are fairly low profile, and it's not like they make a trick any easier. If you smack your head hard on stairs hitting an urban rail, your session is done, helmet or not. Whereas if you take a body hit on stairs with some padding, you might have an advantage. Helmets don't make getting a trick any easier.
Thirdly, the stigma around helmets, from both snow sports and other sports such as skateboarding, creates an environment where kids entering the sport think its not cool to wear a helmet, and that's something that shouldn't exist IMO. Kids especially should be able to wear helmets without being criticized. It's easy to forget that pros are PROFESSIONALS. They know what they are doing, and just because your favourite pro hits a quad kink with a beanie on doesn't mean that you have the same experience or skillset to be able to do the same without getting hurt.
Of course everyone can do what they want, its up to the rider at the end of the day. As for adults, they can make their own calls about wearing a helmet or not, and that's on them if they get hurt. I think parents should make sure their kids wear a helmet though.