Scribe Ineti said:
Published settings (and games in general, for that matter) need support in the form of new stuff to buy on a regular basis, otherwise some vocal gamers start screaming about how the game is 'dead' and that they don't play 'dead' games.
And I guess some gamers need their fix, i.e., new stuff to buy for their favorite setting or game.
I've encountered both of those attitudes.
Support - and it is support, supplemental material that aids the detail of the setting - is something you'll always see. I don't think you can do justice to most settings with just the one book, and there is always significant room for expansion.
Lots of gamers like detail. Lots of crunchy detail, even if it's not rules. I'd be willing to lay money that for every gamer that hates detail, three more like it - it might not be rules detail, but you can be a rules-lite guy and still love details.
Let's look at the Eberron line. The main campaign book is large and very well done. Yes, you could probably run Eberron for five years just off that book, depending on exactly what you did.
Dragonmarked is a support book for that campaign. It offers more details, personalities, and not all that much crunch; it tells you how the various Houses interact with the world and each other, what their plans and goals are, etc. If you're running a game with a lot of House intrugue, it moves from 'nice to have' to 'required' unless you've had a tremendous burst of inspiration.
Sharn might as well be 'Campaign Book II' for Eberron. It's a city so large that it deserves it's own book. Frankly, unless I've had a lot of time and a tremendous clear vision of where I was going with it, I'd never be able to write something as interesting, detailed, and cool as that. I probably
could for some worlds I've done, but it's unlikely I could for this.