Actually, it's to provide a template for the players to tell a story, within the confines of what's provided. A story teller tells the story. In DnD, the players create the story. This is done through choices they make, dice rolls they make, or fail, and how they choose to go about combat. As a DM, you should have an outline, not a play by play, of what's expected to happen. There are around 50 years of lore to this setting, how much are you going to explain, for how long, before other players in your session get frustrated because resources are available. To your "Shar is...", there are books that cover that in game already. At some point, it's up to a player to find/read them. How many dialog wheel style choices do you provide for your players, instead of them organically asking questions? How are you going to code every possible outcome into a cRPG?
Are you seriously arguing that players should have to read D&D lore books if they want to know things in-game? Players are essential parts to a D&D story, yes, but they don't create the world in most cases. The DM does (either making it up himself or using others' worlds) and it's the DM's responsibility to give out that information to the players when appropriate. There are some cooperative game styles where players can make up information/lore/mechanics to incorporate into the world (obviously I'm not talking about backstories here), but that's certainly not BG3.
As has been said, there is a reason that Religion skill checks exist in D&D. It's so that players can make those checks to gain character&player knowledge about the world.
