No one forces anyone to do anything in life. If your roofer aka players screw up then it's just incompetence or malicious behavior which consequences are trying to be passed on to the employer. However, if the employer knows that the roof is screwed up or otherwise dangerous working environment then it's employers fault. The roofers acknowledge the potential dangers of their trade but still engage in their business. If one doesn't like the terms of the contract of employment then just walk away. No one forces these guys to play hockey for their livelihood. They could opt for a comfy desk job but they accept the risks of brain damage done by other players that do not want some less dangerous job. Don't have to act like that these guys are 5yos who have no idea what the risks and rewards are.
When someone says “I’ll pay you a million dollars a year to entertain me with your life” and you know that otherwise you might be lucky to get a job at $50,000 a year because you’ve spent your childhood focusing on a sport and not a career, I think it’s a bit different than what you’re dewcribing. People (players) are easily tempted by large sums of money at young ages and grow in the hockey mindset. Their coming of age is literally with hockey alongside them their whole life. They weren’t adults when they started, and honestly a lot of them stay children in their early adult lives because the life of a professional athlete is totally different. There’s a certain indoctrination of being lucky to be where you are. Few people walk away from the chance to be a professional athlete, and most of them are not very mature when they come of age to become one.
Anyways, I’m not saying you’re entirely wrong, but I do disagree with the idea that a roofer accepting a roofing job is the same thing. Also, the roofer will have himself protected by his employer via health insurance, workplace accident insurance, accidental dismemberment, blah blah blah. Is CTE covered by the NHL years after they’ve left the league? I don’t know the answer to that.
Also the suggestion that the NHLPA would ever agree to a “danger” clause is outlandish. Their role is to represent the young immature player that I just painted a picture of, and they would absolutely not in any way shape or form let such verbage exist in the CBA (and it wouldn't hold in a real court anyways).