You are not the center of the universe, and not everything revolves around you. It's exactly this sort of thing that makes a world feel real. NPCs will have conversations about tangentially related topics or places while you walk by, you'll hear about events in far away lands, and, generally, at some point, something terrible will happen to upset the status quo, bing bang boom main plot, hero's journey, return to status quo. All of this is great
Very few games, though, actually simulate things in their world happening, so everything has to be a cheat (bit of a strong word,) of some kind. Events and lines are scripted around player actions in the main story or sidequests.
Which... As far as I can think, are the only ways players can have meaningful effects on the world in games that do that sort of thing. I'm looking at you, Skyrim's NPC chatter. But we're back to player control. No more talk of that.
NPCs just don't exert control over the game's narrative in response to the player's actions outside of the story. Which games leverage powerful non-players to create a living world, then? There's the obvious answers in Dwarf Fortress and Mount & Blade. I... Frankly can't think of any off the top of my head. Civilization and other slow-burn strategy games? Those shouldn't really count, as the NPC presence is just a replacement for a human. XCOM? The story beats are pre-scripted, but every game is pretty unique. Differences in scale, I suppose. Send me angry messages on Twitter with how X is the best at this. Don't waste time with an Email.
Bringing it full circle, I'd love to have huge NPC Empires duking it out for control of FlyShootTrade's galaxy map while the player flits about and does their little questy-shooty thing, but that... At this point, that's silly to think about.
