The first and most obvious benefit is that it gives us a voice. Really, developers aren't obligated to give players the time of day. As long as their bosses are happy with them, well, that's all they really need to be concerned about. Of course, said bosses aren't going to be happy if a developer decides to absolutely destroy some vital feature of gameplay and the players respond by unsubscribing.
We've talked about voting with your wallet before, and this is what allows us to do precisely that. If a game was launched that had A Vision, and it cared about that more than how much money it made, unsubscribing wouldn't make an ounce of difference. This was one of the complaints classically leveled against City of Heroes while Jack Emmert was at the helm -- something that didn't last forever, which can be speculated on left and right.
There's not an absolute scale, of course. Fallen Earth's developers have a vision for how they want the game to play, one they stick to because their subscriber base is happier with most of the game as it is. And how do they know that? Because the subscribers say that they're pleased with the game, and the subscription numbers back it up. Voting with one's wallet works both ways.
Being in it for the money also is part of why we get some of the nifty things we all but take for granted. The whole idea of microtransaction stores comes about because, well, the developers want to get more money. Since we won't just pay money for nothing, well, we get little additions to the core game. City of Heroes and Champions Online have both capitalized on this in notable ways, offering a number of customization options for purchase in the store. How much they're worth can be debated endlessly -- but without the incentive of "these will make us money," it's unlikely most of them would have even been created.
Expansions? To make more money. Extra content? To make more money -- after all, patching in a major content update means more for you to do and more incentive to keep playing. The whole idea of having content updates that cost nothing and are simply added to the game is more or less unique to MMOs -- at best, other games might have one or two bits of donwloadable content that were features cut from the game at launch. (Or they'll expect you to pay money for it, at which point we're right back to "they're in it for the money.")
That's not even getting into the reason that many games have the development budgets that they do. Cinematics, modeling, textures, et cetera -- all of them cost money to make, and more effort is going to be spent on something that investors think stands a reasonable chance of making money. Allods Online is being received with awe by many gamers because of the high production values on a free-to-play game -- which exist because it seems likely that the game will make back the development costs. The fact that we prefer games with higher production values makes the entire investment process a double-edged sword, but one that gets us better games in the long run.
Of course, all of these reasons get at the core of the problem -- the phrase "they're in it for the money" is associated with the idea that they're just doing it for the money. That how good the game is really doesn't matter to them at all, and the unspoken assumption that fans would do a better job of running the show.
Leaving aside the debate about whether or not people who love something are the most qualified to manage it, there's the simple fact that nobody gets involved with the MMO business without first being interested in the field. This is not investment banking. Successful games do decently, but they're not outstanding. Many games don't. There's a reason why many developers have blogs and talk to the community -- because they started as fans and got into the industry because of that.
You can love something and still make money off of it. Heck, the job of covering MMO news and opinions -- it's a job. It's work. We do it because we love games in general and MMOs in particular, but the volume of our posting is because we're here to do a job. And, yes, make money.
And the thing is, more often than not, when you make money by doing something? You start caring about it more, not less. It stops just being what you're doing to have a laugh, and starts being a skill that you owe it to yourself to practice and refine. Something you need to learn more about, to get better at, to develop. I'd wager good money on the idea that every single developer is happy to be working on a game, proud to go into work every day and get paid to do something they love.
They're in it for the money. Good for them. Good for us.