Hussar said:
Well, for one, you've certainly got tradition in there. Other than 2e, every edition of D&D has had a default setting.
I don't think that's very true. While 4e did and 3e did, 2e
sort of did (The Prime Material world your games existed in wasn't very strictly defined, but it was clearly part of the greater planar structure), 1e only
kind of did (if you consider things like assassin's guilds and druid circles to be world-specific), and OD&D pretty much purely didn't (the original boxed set references setting games on Mars/Barsoom and keeps monsters and PC's very generic, mechanically). And 3e's touch was light -- there were some Greyhawk proper nouns, but nothing very funcitonally "Greyhawk," and 3e was the only e so far to include alternate cosmologies and planar structures.
So it's a muddier history than that.
Hussar said:
Secondly, a default setting dramatically lowers the bar for new entry into the game. If you have to build a world before you can play D&D, you've just turned off a whole lot of new players who simply don't have the time/energy/inclination to world build. There really are players out there who just want to sit down and play.
And why can't those players be served by a fleshed out example?
The distinction between an example and a default is kind of subtle, but pretty important. One shows you how to do it (and can even be usable out of the box), the other carries with it the assumption that this will be used automatically.
Hussar said:
What's a slaad (not to dredge up that can of worms) without Limbo or any connection to the outer planes? What's a modron? What's any outer planar creature without some sort of default cosmology? Heck, without a default setting, what's an elf? or a dwarf? Or some of the less mythical style creatures like orc or dragonborn?
They're all great examples of particular kinds of races or creatures a DM can opt to include in her game. They don't need to be assumed to all exist and be the same everywhere. The story of the slaad is one possible story of this one possible creature in this one possible reality, not a necessary bit of fiction for every D&D game. It's a good story, and it should be presented with respect for its good elements, so it doesn't need to be changed, but presenting the whole story as an assumption rather than and option or example is a problem. The core rules should really, I think, recognize that the function of lore and cosmology and setting stuff is to
make the DM's job easier. Examples and options do that. Assumptions a defaults do not do that as well.
Maybe the distinction I'm making can be a bit unclear, so let me give an example.
At one end of the continuum, you've got 4e's monsters-on-a-business-card: raw stats, no context, roll your own, pure math. If that's all the game gives you, it's not great, since they're leaving a lot on the DM's shoulders.
At the other end of the continuum, you've got, say, 2e's Time of Troubles, and the expectation that all DMs everywhere must follow this proscribed canon. If the game wants you to adhere to a canon, that's not great, since they're speaking for what should be open to each table.
What might be better is that, say, WotC presents the Time of Troubles as an example of a world-shaking apocalypse that can happen in your games. It's there and it's fleshed out and it's something you can easily do and it might even be something that WotC tries to persuade everyone is the hottest thing since azers. You make it easy for people to use the material, but you don't assume that the material is going to be used by everyone.
It's not that D&D should have no setting. It's that D&D should have examples of myriad different kinds of settings, and not assume the use of any one as a default. No default, lots of examples. Like the monster manual: full of lots of monsters, but not assuming the use of any particular monster. Here's orcs. Here's hobgoblins. Here's gnolls. Use one, use none, use two, make your orcs hyena-loving or whatever.
Cosmologies should be the same way. Here's Eberron's Orrey. Here's Greyhawk's Great Wheel. Here's Spelljammer's Crystal Spheres. Use one, use none, use two, put your crystal spheres in the great wheel or whatever.