Do rugby players suffer concussions as frequently as American football players? If they don’t, could the helmets be making the problem worse - encouraging players to hit with their heads more, like a false sense of security? Sorry if this is a stupid question, I don’t know anything about American football and not much more about rugby!
EDIT: it seems like rugby players are more prone to concussions than NFL players, but I might not be completely off the mark about helmets offering a false sense of protection:
“Rugby players are believed to play more aggressively when using scrum caps; however, studies have shown these make no difference for protecting against head injuries.”