I want lots of content in my premade settings, and I don't want huge nebulous blank gaps in the map (if I want a blank map, I'll homebrew) but I want it at a reasonably high level. Don't detail the name of every innkeeper, or indeed every inn. If I'm running a game, and the PCs go to the city, I'm not going to remember the names of every shop they go into or every street they might decide to wander down, and I don't want to either have to cram my brain with every possible NPC before each setting, nor do I want to be continually referencing the setting book in play to avoid going off-canon (because if you use a detailed worldbook, the players will know about it). Cover the high points, general info about geography, rulership, attitudes, important locations, power groups, sources of conflict a few bits of local culture for flavour, local monsters etc, maybe a handful of important NPCs. Beyond that, cover any important organisations that span geographical regions, deities and how their religions/worshippers operate. Give me an array of possible warlock patrons for various different pacts, and what they might want from their pactees.
I can invent basic NPCs on the fly, don't worry about giving me the statline of every guard or streetsweeper. But give me ideas. Give me organisations to work with or against, give me plot hooks and adventure locations out the wazoo, give me NPCs with motivations that might work with/against/at crosspurposes to the PCs and give me plot hooks pertaining to them and some material I can practically use about how they operate.