The arguments above are all making some good points, but I argue that they're blurring together wholly unrelated considerations.
1.) Modding will work for any game if that's what the game is designed for. Modding will fall flat for any game if that's not what the game is designed for. It's really that simple. This is exclusively a design and development decision. [This is the only consideration that concerns modding.]
B.) A totally separate consideration is company PR. Even if I have an amazing game, poor PR and customer relations can destroy my game. Reputation is huge in determining popularity -- but popularity and acceptance have absolutely nothing to do with how good a game is
in-and-of itself. It simply means that a garbage game might be played by a lot of people, while a brilliant gem of a title might go completely unrecognized. [Notice how modding was never once mentioned, because it has nothing to do with this.]
and
#.) The success of a game is not determined by "how much money it makes". Its
financial success is determined by profits and ongoing revenue. That does not mean that a
tremendously successful game (in terms of
innovation,
gameplay, and
player response) cannot be given away absolutely free and never generate a single dollar. They are two, totally separate concerns. [Neither one of those concerns has even the slightest thing to do with modding, directly.]
Now, comes the endless tug of war between different people involved in the system, each with their own agendas:
- In certain cases, investors and producers will overstep, and a beautiful game will be severely damaged or utterly destroyed when the design and development is derailed by individuals that do not care about the experience as much as they do about their profits.
- It's perfectly possible for overzealous designers and developers to overreach and create a title so amazing and involved, that they'll never be able to afford the development and it will never be delivered.
- People on either end may fail to realize the vision of their game, and it will harm a project because the final product doesn't gel and...just...isn't a very good game.
So, how is the decision about modding made in the best way possible? The designers and developers -- the people with the vision -- the ones working day-in and day-out to realize that vision -- use their expertise to decide whether or not their game will benefit or be marred by modding. Then, they do what they know to be best.
Can't please everyone. That's not even a consideration. That's wavering.