Because it arguably violates the
Personal Conduct Policy just as much as some of the other cases that the league office investigates.
Says who? It's a part of the game. It may be an ugly part at times but it's undoubtedly a part of the game, and it's an accepted part of the game. What happened when Dez and Patmon got into a fight? Posted on the team website so everyone could see it.
http://www.dallascowboys.com/video/2015/08/02/dez-bryant-tyler-patmon-fight-full-video-reaction
If you want to try and squeeze it into the Personal Conduct Policy you might have a hard time doing so without getting past the first sentence.
“conduct detrimental to the integrity of and public confidence in the National Football League.”
Fights between players on the field are not detrimental to the integrity of the game. They happen in all sports and they're basically league sanctioned in the NHL. Fights on the field are also not detrimental to the public's confidence in the NFL. Watch the videos and you'll see that most of the crowd loves it, just as hockey fans like to see the gloves come off.
If it were up to me, cheap-shot punches between plays would get my attention as detrimental conduct before off-hours pot-smoking.
The relative amount of wrongdoing associated with either is irrelevant. Should players be punished for pot? I don't really care. The NFL will likely not remove all repercussions from that activity until it's legal on a federal level. Until then it's against the rules.
Should players be punished for getting into fights at practice? I don't see why they should, but I wouldn't really shed a tear if the NFL decided they were going to punish players for it. I think punishing them would be a waste of time, and may actually be counterproductive. Rather than vent or lose their cool in a supervised environment while wearing pads, who's to say that players won't hold onto that anger and follow a guy to the parking lot where no one really knows what happened?
It's a physical game full of emotions and pride. They are inevitable. You can't ask a guy to battle in the trenches day-in and day-out and not expect someone's tempter to get the best of him. If you watch the video from Dez and Patmon, you can see that neither player was even concerned with the fight afterwards and both guys had already moved on from the incident.