Players don't care. Or at least they don't care as much about your campaign world as you (the GM) do. I read that in a DnD Dungeon Master's Guide once, not sure which edition though. It took me a long time to understand what it meant though.
Pro-tip: It means more work for you (the GM).
I had a rather robust talk with Eric the other day about GURPS and we discussed how easily he gets frustrated with campaigns and how his always seem to fall apart and get left behind unmourned. He cited his latest campaign as an example, we played once or twice with 4th Edition DnD and didn't even get through a whole scenario. Then we cancelled it for the GURPS thing he's working on now.
GMing can be a hard and utterly thankless job at times (especially if you're crazy like me and absolutely MUST have everything written down beforehand). Player's will ignore plot hooks and they will decide to kill the NPC you've spent the most time writing a background for and they do both on any little whim, that is their nature. They're players and generally they care about their characters more than the empires and NPCs you've put into the game. They want to do stuff and that stuff may not necessarily have anything to do with all the neat stuff in your world.
In short, you (the GM) have to make those homicidal/sociopathic ADHD little shits care.
I will cite Eric's campaign as an example, as I was a player in it. I know he put a fair amount of effort into it because I was right there with him talking it out and going over details and timelines with him. What I say now I do not say with malice, I found his world totally forgettable, and not because of the beets (or the lack thereof). I didn't feel like I was a part of it or that there was any depth to it, I felt like a sociopathic, robot, ADHD motherfucker. So I acted like one.
My players are notorious for not reading background material and not remember names and places. They just don't pay attention or care enough to pay attention as much as they need to or take down notes on a regular basis. At one time that would have brought on fits of GM Rage, nowadays I put on my big boy pants and create ways to sidestep what I perceive as their inadequacies. They never take notes or remember what happened last time? Logbook that I force feed them every scenario. No one does backgrounds? Backgrounds now provide in game benefits. No one cares about the details of my world? Hit them over the head with stupid little details about my world every chance I get and write out Walthuler missives.
Anyway, back to the point. To me, Eric's campaign was forgettable because I didn't feel like Junkpile was a part of it. To make players care you have to make them part of the world. You sometimes have to do stuff like call them by their character's names when you're at the table or fill their heads with useless bits of information about your world. Sometimes you have to drag them (kicking and screaming) into your head to roll polyhedrons. If you don't put your all into the game and the world, they're going to pick up on that and respond in kind by not caring too much.
My wife tells me that I get so passionate and amped up about DnD that she almost believes she could get into it with us. Not because she is intrigued by steampunk technology or wonky magic, but because I am so intrigued by it that it kind of infects her with my passion. I think that is the way GMs have to be, at least the kind of GM I feel I'm trying to be. You need to be the dork that won't shut up about his favorite deck/book/save file/etc. You as the GM are kind of the lens the players see the campaign through, so if every word I say or write about The New Empire is tinged with my contempt for the nation, the players are going to likely have a lot of contempt for it as well because all they know is the information I present to them.
I guess what I'm trying to say is a kind of given. If you're making a world, you need to find a way to make the folks wandering around in it see it as more than a collection of statistics that act as a loot and gold dispensing machine.
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