MarkB
Legend
If the DM cannot be bothered to even decide on a campaign setting, that is not a DM I would like to play with. This has nothing to do with player input, or talking to the table, or player style. I just want to make sure that my DM cares enough to at least decide on the world that we are playing in. Because if a DM can't even make that single decision, and farms it out to the table, that bodes poorly for the play experience. IMO. This doesn't guarantee a good DM, but I'd never play in a game where the DM can't be bothered to select a campaign world.
For some DMs it's not about the setting, or even the storyline. Just as you suggest players creating stories within the interstital spaces of the campaign lore, some DMs - some of them good ones - like to spin their narrative out of the backgrounds and interactions of the characters. And they will be fully invested in those narratives, no less so for the fact that they came up with most of them on-the-fly based upon a few off-hand remarks and character interactions rather than planning them meticulously in advance.
And if they know that's what they're ultimately going to be doing for most of the campaign, then they're really not going to be too concerned about nailing down its starting point.