Without gambling there would be no upsets. The best teams would continue to win over and over. The league would take a nose dive and become what hockey is to the US. The die hard fans would be the only thing keeping the nfl on life support. The NFL needs gambling. It was founded for gambling so it isn't going away.
SI NFL survey from just a few weeks ago claims only 8% of NFL fans bet with a bookie or online. I think it's 16% or so bet with a friend.