Remathilis
Legend
2014 I can see, but WotC didn't use that because they were still trying to push the multiverse. The elf section doesn't talk about sun and moon elf culture, or strongheart and lightfoot cultures for halflings. We get some human ethnicities but they are divorced from the lands they dwell in, the enemies and allies thru live with, the Gods they worship and the languages they speak. If you want to make that stuff matter mechanically, you have to intertwine them with the PHB so that Rashimi has the context to be understood without the Forgotten Realms duology of supplements.Forgotten Realms. I thought that was quite obvious. Given, y'know, a third or more of all the books really are about the FR and only incidentally about anywhere else. And the fact that the vast majority of adventure paths and such published by WotC are specifically set in the Forgotten Realms.
And 2024? They put a freaking Greyhawk gazetteer in the middle of the DMG. Maybe if that that been the Sword Coast, they could have sprinkled culture elements throughout the rest of the Core and tied it all together. Alas!