Wrote a new blog today about how much setting should go in a rulebook. It's different for every game, but I feel a lot of games put too much lore in with the rules.
I know it's really hip to have your setting lean on your mechanics and vice versa, so neither works great without another, but I am more of a fan of rules that support tone and play patterns that reinforce genre more than specific settings. Probably mostly because I am not big on learning a lot about a setting before I feel good about running a game.
I also like to have lots of room to improv and make a setting my own. I know you can do that with any setting, but I just feel more confident doing that with less definition in the setting.
I could probably drop a little something more into my rulebook as a stinger to get people excited about what kind of fiction the game presents. I guess that could be interpreted as setting, or at least adjacent.
I sort of agree, I have never played in a premade setting except for a 2-shot for city of mist and I've never GMd one at all, and I often spend a lot of time reading rulerooks for ideas for my own RPGs.
I've been trying to write my own collaborative storytelling game recently rewards players for taking on a storyteller role but doesn't stop players who would prefer to remain as one character for the session, and when I read Ben Robbins' blog post about Remember Tomorrow, I thought I could use a part of this and bought the pdf. I'm trying to build a royal court political thriller type system and I know that this was cyberpunk by default, but 3/4 of the page count is really guidance on how to make a specific tone of cyberpunk lore, with the rules interwoven between them.
I feel that if your system is novel and applicable to many tones and genres, it should be seperated from that genre any related setting in the rulebook, and similarly if you're rules and genre are wrapped up, it's a good idea to seperate setting slightly, which we commonly seen in fantasy RPGs.
I feel they should be in the same book, but unless your rules are absolutely dependent on your genre or your the two absolutely dependent on your settings, it's wise to seperate them to make your book more easily usable by those wanting to work your ideas into their own.