If this were some standalone IP, I'd agree 100%. The problem is, "the world" is Dungeons and Dragons, not just BG 3. There are 10s of thousands of stories that are part of "the world" that may not have any impact at all on BG 3, and every time I see "there's a disconnect", I wholeheartedly agree, there is a disconnect. People are always trying to disconnect BG 3 from the thousands of years of history in the Forgotten Realms. Or, more accurately I guess, they want that history outlined for them, because this is the "assumed knowledge" that the characters have, or that some of them will have. In the case of people that have no knowledge at all about the setting, yes, they should be hitting "outside" resources, because the outline could be a real slog to sit through.
Even though DnD is becoming more popular, we can't expect everyone to be familiar with the setting or to want to do outside research. Too much work to understand things will make for less sales. Basic information should be given to the player, more detailed information should be found in books. If the basic information was offered with a mouseover then it wouldn't clutter up the screen for those who don't care about it or already know it.