I remember reading that Giants fans think it is barbaric to scream the whole game. They tended to look down their nose at fans like the Seahawks, who do. I remember Coughlin and his team trying to get the crowd more involved, but I just don't think the current fanbase wants any parts of that.
I am not sure about the Jets fans, but from reading Riley's experience there, sounds like they are of the same mindset. I think it is the sit down vs stand up crowd. Some fans want to watch a game, others want to experience and feel part of the game. The purist still feel that all the noise stuff is just a small blip in the actual game, though you may have a hard time convincing those who watched the first snap of the SB.
Just like Steve Young screamed after winning his SB, no one can ever, EVER take this away. As Steve Mariucci said about the griping from the 9ers vs NY Giants playoff win, "Bummer".