In my younger days, I would write a full on campaign history and back ground information. What was worse, I expected players to read that stuff. I learned that they weren’t interested in reading my pile of made up history about a made up place.

Game masters, I’m talking to you. I do not want to read a 6,000 word history of your setting. I don’t want to do home work to play in your game. I want to show up, pull out a character sheet that took me 15 minutes to fill out.  I want to play. I want to laugh, I want to feel nervous, I want to feel elated when I roll a nat 20 at just the right moment. I want to feel a little bit sad when a likeable NPC dies horribly.

Do you know what I’m going to remember 20 years from now? I’m going to remember that time when we were sitting around the table laughing about that silly NPC that had a punny name. I’m going to remember when that NPC I liked died and made me a little sad.

I’m going to remember when the entire party nearly died, but then the wizard hit with his dagger and rolled 1 hp of damage but still killed the dragon.

I’m not going to remember that clever little bit with way the you blended the Indus Valley civilization with the Sumerians and Atlantis to create the ancient civilization whose we were adventuring in.

You can world build. You can history build. Go nuts. Do it for yourself. It does help to make your world consistent and improves verisimilitude but you probably won’t remember any of that shit in 20 years either.