Let's review an ordinary scenario.
Freddie, our typical gamer, takes a trip to California, and while out there he stumbles into a little hole-in-the-wall gaming store. And there he finds a new RPG, something that isn't even on the net, that looks amazing. There are ten books altogether and since he's on vacation and has a budget for weird purchases, Freddie buys them all.
He spends the rest of his vacation and the week after devouring his new purchases and come the next gaming night, he's ready. "We're not playing D&D tonight," he declares. "We're playing Zombies & Musketeers!"
And so the rest of the evening Freddie explains how the game works, how they have to roll characters, what they're allowed to do, what they're expected to do and basically the fundamentals of why this is a better game.
The reasons for this change is obvious to everyone. It's new. When anyone cares to examine what's going on, or question is (as one player probably will), the fact that Z&M is new will no doubt be the trump that's played.
I, however, find myself wondering if it's really that Z&M is 'new.' Looking back at incidents like this, I think it might not all be the zest for novelty. I think there might be an entirely different emotion at work.
Consider. Freddie, our example, has had two or three weeks to indoctrinate himself in depth in the subject material. As the referee, Freddie is in a unique position vis a vis the new game - he's seen it. He's perhaps experimented with it a bit, and if he's given himself a good couple of months to really examine it and build up a campaign for it, he's the BIG EXPERT at the table, isn't he? Freddie may not be the brightest bulb in the lab, but for at least a couple of months, he's a step or two ahead of his players by default. He can lord his special, intricate knowledge of Z&M over the others ... at least until the others get a chance to look at the rules, to figure out how to play them. Lo, three or four games down the road, the players will start to challenge Freddie's mastery of the game, and after that its all much harder work for Freddie.
But perhaps he can find a new game to play after that.
There may be a great deal more to the ever constant 'new campaigns,' 'new editions,' and 'new games' that act as a tonic upon those for whom roleplaying games are a commercial sport. Having the edge on your players is something you certainly gain when you change the rules on them every six months. Then the players are kept steadily off balance, and you, the DM, get to enjoy those brief periods where every question can be answered with a de facto, "That's how this campaign works."
Sooner or later, however, your players wise up, begin to figure out your new rules, and start using them against you. This is the worst thing for a dictator. You've got to do something. Close your campaign and start again.
Seems to me I remember a steady stream of people once upon a time who always had a 'new game' they'd just picked up. There seemed to be a certain pleasure they had at outlining how everything worked, while their players wallowed around in uncertainty and unclarity. For some of the gentle readers who are scoffing as I write this, I should point out that this sort of behavior - the old salt lording it over the newbie - is extremely common. Some people really enjoy fucking newbies around ... and changing the rules on the newbie for the first few months on the job is one of the best ways.
Working in restaurants, we used to send new servers off to random tables with plates full of bacon, only to laugh our heads off at them standing in front of uncomprehending customers wondering what this server is doing. We would send young boys off across the street to other restaurants to borrow their banana peelers, or tell new dishwashers some odd item got 'put in the basement' ... so that they would wander around trying every door, looking for the stairs. These are the sorts of games every industry plays on every poor newbie stupid enough to start working there, or stupid enough to be young.
Are you so sure that the RPG'ers new! new! new! chant isn't just another way to fuck people over?
After all, if you can't control the rules by virtue of being the only one that knows them, than you have to play by the rules. Your players will keep you honest. Which means if you're going to stay a jump ahead of your players, you'll actually have to be more creative, more insightful and more clever than they are.
I don't doubt a lot of DM's just aren't up to that.