AbdulAlhazred
Legend
Is it always as absolute as that, though?
Sometimes, e.g. in a sandbox-style campaign, there doesn't really have to be a story* at all for play to begin and in fact it's the game itself that does the work to build a story as a simple telling of the tale of what the PCs do/encounter/say/etc. over time. It's story-after.
* - beyond a simple static background with no ongoing plots behind the scenes.
Now if you're talking about story-first type of campaign e.g. a hard AP then yes, without the pre-authored story the game won't accomplish much.
And even in story-now you are, like with story-after, building the story as you go along. You say that without a story an RPG can do no work, but in two of three possibilities (story-first, -now, or -after) the work of the game (and the people playing it) is in fact the building of the story. Only in story-first is the story built...well, first; leaving the actual run of play with a lot less work to do.
Lanefan
Eh, I don't like to actually get into a deep analysis of the mythology of the 'sandbox', because it raises so many hackles, but suffice it to say that I think this is theorycrafting. The GM is always building stories. He may be letting them lie somewhat passively, but even sandbox GMs constantly ask themselves "how do I push this thing forward?" At best they may be neutral in terms of which way it goes forward, but they're never satisfied with just leaving lie. Every tavern has a tale, every library has a dusty book (that the PCs will likely be the ones to find), every court has some sage with a story about this or that lost McGuffin, etc.
Why is it always the PCs who find these hooks, and they weren't long ago exhausted? Because the GM needs a STORY! Why do the PCs always (almost always) stumble upon a level-appropriate adventure location? Because it wouldn't be interesting to tell the tale of them getting slaughtered by 7HD monsters at level 1! Why is there always some easy beginner dungeon an hour's walk from the town (B2 please stand up)? Right where every greedy git would be able to find and loot it? Because we need STORY!
Sandbox is a way to be coy about setting up and running the story, but its still fundamentally story-oriented gaming. I put it as, in real practical terms, not theory, as a subcategory of 'Story Before' (though I don't think I like these terms, 'classical' play seems more like 'Arranged Story' vs Story Now being 'Developed Story' or something, but I quibble).
Anyway, I get what you're saying, but I really do think that when you get down to actual play, if you were to analyze sessions of play and what was happening, and why, and what the actual roles of the participants were in practice, vs theory, my assertion is that you'd find creating story, and driving the game with it, is quite important. In a sense even Gygaxian play has story as a central theme. I mean, why do the players care? Why is advancement of the characters meaningful? The very fact of level names and name-level domain rules and such signifies that somewhere at the core of it is trying to enact a kind of tale. None of this is surprising either. Even very abstract games like Chess actually come with a story attached. Story is so fundamental to everything to do with human thought and experience that it cannot be anything BUT central to play.