An NFL player has 2-3 years usually, 5-6 if he's lucky, more if he's really lucky. We only hear about the ones that make it. There are over 17k college football players, of that only 200-300 get a shot at the pros and even fewer make it. The ones that do are almost always injured. They give their bodies for the few years of play for our enjoyment. The owners have no risk, they just keep raking in the cash, the NFL makes billions. The majority of the money should go to the ones getting their bodies destroyed on the field.
Now I'm not saying their aren't very greedy players out there, there are many. Guys that want a new contract after a year of play. Also, with guaranteed money up front, they are reducing the risk of getting cut. But that's just the super stars. There are a lot of guys that just play a few years and get beat up. Get cut with no guaranteed money. Don't make it through a camp one year.
I look at Desean Jackson, from the Eagles

It's just my opinion, and there are certainly situations where players are fools and greedy. But in the whole I have to side with the guys risking their bodies and their livelihood every week. The 18 game season proposal is just crazy, to me it just shows that the NFL just thinks of the player's as tools.