Rugby is having the same discussion as well. Despite the lack of helmets, there are comparatively few skull fractures but the incidence of CTE is way too high. The insidious problem is not so much the big hits, but the accumulated result of "microconcussions", lots of small hits, something that rugby is more prone to than US football AIUI.

Alix Popham's story is particularly poignant:

https://www.bbc.co.uk/news/articles/c2kgjdxxz7qo