I enjoy working on my setting. I also enjoy gaming. The setting is not anathema to gaming, and since most of it is written with 3.5 in mind, gaming functions rather well in the setting.
It may not be anathema to gaming. But it might not support it as well as a setting that is extremely mutable.
Let's say you've previously established that in the last 200 years, no one has ever gotten in to see the king without a 6 month waiting period and during that time dragons attacked neighboring kingdoms and the king has always refused emergency meetings.
Now, the fate of the world lies in the PCs hands. If they fail, Tharizdun(or whoever) is going to be released and kill everyone. In order to build up a sense of urgency in the plot, you've established that the Ritual will be completed tomorrow. But there is no way they can assault the fortress without an army helping them and the King has the only army.
In a mutable game where you have no idea who the King is or what the rules of the kingdom are before you start playing, you can make him a benevolent King who will help them out when they ask. It fits the story better, it causes the campaign to end in a climactic fight between the good forces of the King and the evil forces of the fortress.
I'm sure in a campaign with a set world, you might be able to avoid the situation. You might have someone else with an army who will help and a system of teleportation gates that let them get here on time, you might never write that situation into the plot because you don't want to blow up the world. However, if the situation DOES come up, you need to change your world and sacrifice consistency and realism in exchange for playability(likely ending up with the King changing his mind, strangely, since he never has before). Either that or you have to sacrifice playability in exchange for consistency(which generally means the bad guys win and the PCs have to deal with the aftermath...or they all die and start a new campaign).
I enjoy the idea of gaming groups having an impact on the setting. I also enjoy using it as a setting for writing. These two can co-exist in the same setting without instancing.
They just have different goals, that's all. The goal of a game is to allow the players to have fun, often while letting them be the heroes. The goal of writing is just to tell interesting stories.
Often the things players find fun aren't interesting stories for anyone not participating. Often the interesting stories are not fun for the players because they focus on people other than them. If you have extremely cooperative players, you can have adventures that don't focus on them.
I just know that if I had another adventuring group solve the problem for them, or even told tales of another adventuring group who did better things than they did, they'd either be annoyed or not care at all. So it would either make the game worse or simply not add anything to the game as it doesn't make it more fun for them.
Thus, the different focus of the two approaches.
I believe there was a quote that said something to the effect of "my game is not your playground". But from a player's point of view, I don't play in order to be forced to play in YOUR playground either. I play in order to get a chance to use my cool powers, role play my character, defeat my enemies, accomplish my goals, and become a hero.