Yeah, I completely agree. American football is a very rough sport. That's why it takes such strong people to play it.
I am curious though, how do field-related injuries have anything to do with those players drunk driving?
You should read about alcoholism and its effects as a coping mechanism. Albeit every American sport has had this problem since the 70's. Hockey for example: Derek Sanderson of the Boston Bruins nearly died because of his problems with drinking and this was during a time when alcoholism wasn't even addressed.
Player fitness and conditioning in sports has been on the rise of course. I'd say hockey players are the toughest conditioned, but you can't be a complete pusillanimous individual to spend 90+ minutes in humidity running/passing/and getting into scoring position in soccer. American Football is less action because there's brief moments of intense activity then breaks, and you especially notice this if you've ever been to a pro game.