RIP Jason Hairston It has only been in the last decade or so that modern brain research has revealed the very serious and deleterious effects of repeated impacts to the head which can lead to CTE over time. I recall old school coaches actually instructing defensive players to "put your helmet on the ball" as a method to try and jar the ball loose from the ball carrier. Teams also routinely gave out "hammer awards" for the most violent hits in a game and concussed players were often expected to "shake it off" and reenter the game as quickly as possible.
We now know just how dangerous all that was and the rules of the game are changing to help protect the players and strict concussion protocols are in place for all sports. We will continue to see more rule changes in the future to help protect the players, such as the possible elimination of kickoff and punt returns, and, hopefully, we will continue to see significant advances in safer equipment for the players as well. We will never be able to eliminate all the risks of playing any contact sport but it is imperative in this day and age that we always move forward with the best interest of the the safety of the players first and foremost before all else.