I never thought he would retire. All the "this is it for him" talk seemed like talking heads manifesting more than reality.
To be 100% honest, if I were him I probably would not retire either despite the obvious risks. People do far more dangerous work every day for a hell of a lot less money.
I would probably talk myself into taking additional steps equipment wise, playing the game a bit differently to protect myself and buying into the idea that a lot of it was just bad luck.
Plus Mitch Morse and other players have continued to play at far more physical positions where the risk of smacking helmets is almost 100%.
Not saying it's the "right" choice but it's his identity and his career. I wouldn't be able to walk away and would have to be told no by the team and league, which is not going to happen for obvious reasons.