Head injuries are common in some sports. At one time taken as just a part of the game they are now regarded more seriously.
A feature is that in sport, especially professional, not only have the players become more physical, the people playing them are bigger, more muscled and gymnasium trained.
This means that they hit harder and with more effect.
This article in the Engineer magazine goes into the subject. In many sports the nature of the game as it is being played at present and by whom and at what age is being questioned.
The sports of today are mostly of recent origin in terms of history. It may be that they could go the way of past sports.
Where's my horse and jousting kit?