Personally, I quite enjoy standing and cheering our team after every big play, singing the fight song after every score, screaming my head off while the opposing team has the ball, feeling that rush when the noise causes the other team to get a false start or delay penalty or have to call a timeout, and singing Rammer Jammer at the end of the game.
Fans are a part of the game and can have an effect - albeit a relatively small one - on the outcome of the game.
If you want to sit on your hands and not actually participate, well - as I said - that's your prerogative.
There's an older couple that sits right in front of us at just about every game. They don't really cheer and miss quite a few plays because they rarely stand. And he spends a fair portion of the game covering his ears because of the volume of my wife and myself. However, to their credit, I've never seen or heard them complain about it.
Personally, I don't understand the draw of being a "lazy fan" at the ballgame. If my age, attitude, or other circumstances were to prevent me from actively participating in the game as a fan, I'd just stop going.
Of course, I'll probably die before that happens...