Well, that's kinda my point. When you start with, say, Forgotten Realms, you can lean on the fact that your players probably have a decent knowledge of the setting. Or, at least it's far more likely that they know about elements of Forgotten Realms, than, say, Cerilia .
Which becomes something of an issue in play. You want to bring the setting to life, but, you also have to actually run the adventure, balance out what the players are doing, and juggle fifteen other balls. And, in the face of that, you have player apathy over the details of the setting itself because they are far more interested in their own characters and whatever the group is doing right now.
I mean, recently I started my Ghosts of Saltmarsh campaign. I expressly told the group we would do character generation as a group. Session 0 starts and every single one of my players already had a character made, complete with background, NONE of them actually referencing the campaign. Drives me up the wall, but, hey, what are you going to do?
This is a problem I've been dealing with across many groups and ages. Trying to ground groups in a setting is HARD and often somewhat akin to nailing jello to a tree. I remember back when trying to get the group into Scarred Lands and having EXACTLY the same issues.
IME, most players do not care at all about settings. All the hoopla about blowing up settings and setting fidelity and "distinctness" of settings is all in the DM's head.
Agree, but here is some difference between FR and greyhawk that I personally see if a player wants to be more invested into a settings lore.
E.g. a player of a cleric wants some more background on his deity
FR: I can point him to FR wiki or whatever, but afterwards will eventually be bombarded by questions like
"What happened to the deity during spellplague /sundering/ the times when they became all mortal etc etc and how do you run your setting considering whatever has happened then?" If I dm my style with heavy restrictions / some housrules then I run into a the situation that I have to clear more things up in the end than if I had told hi mall the background stuff important for my version of the FR upfront.
Greyhawk: I can point the player to canonfire and he gets a bit more background and it fits even if I heavily houserule my greyhawk setting, put in a different tech level, and set the thing to year 579. There might be some contradictions but normally there are none.
Why is that so? Because FR is timeline heavy in what ever (official) lore is referring to what period. It might be that officially the deity for whom my player wants to play a cleric is dead during a certain period.
I Greyhawk the most likely background info my player will find is what kind of people are worshippers and in which regions, what are the colors, symbol etc. maybe some antagonist of the deity, but not much that is connected to the metaplot like in FR
e.g. like god xy killed your god during the spellplague and it was only after the resundering that she reappeared with lost Abeir returning yadda etc... (just makin up stuff here but that's the kind of issues which might occur)