I agree, but it's the same problem we now get with Star Wars; once upon a time, a movie would stand on its own self-contained story, now it seems a lot of the plot is explained by the books / comics / cartoons you've never actually experienced. Some might call that progress, personally for me it's laziness in terms of crafting a good, self-contained experience.
Anyway, on topic, ... I've always felt the Forgotten Realms has always suffered from this problem! I own the original boxed set, and have recently re-read it (well, skimmed, it's not designed for reading end to end) - it feels like a reference book where half of it got left behind, all sketch, no real meat. Then you read for example the first three Drizzt novels to learn about the Savage Frontier, and so on. What did that boxed set tell me about Cormyr? Very little, from what I recall, the only bits with much "meat" were the Dale Lands, and even that was sketchy at best. It wasn't until 3.x put out the Forgotten Realms hard-back, that people finally had a "one stop shop" that, to a fair degree, actually gave you a comprehensive look at the whole land. So more like the old World of Greyhawk boxed set, but not really (more detail, I think, in some areas at least). It's a large reason I've never liked Forgotten Realms... too much material spread all over various products (hardbacks, adventures, novels, even computer games).
That said, I've run a PC in various Forgotten Realms games, and am DMing FR myself now, and we all treat it very superficially - at most, google some basic things, and just run the game like we would normally i.e. the overall game world isn't a huge feature. For example one of my latest PC's was an Eldritch Knight from Cormyr, I'd done some basic research, but we played Out of the Abyss, so I might as well have been from anywhere or nowhere it hardly ever featured at the table.
