Yeah, I remember reading books in the 80s that were all about the setting too -- Clan of the Cave Bear was a big example, about the tribes and stuff like toolmaking and finding herbs and hunting. Thorn Birds was about the forbidden romance &c &c but also had a lot of Australian background in it. Writers would work up a topic and do heavy duty research into it, although that often led to heavy-handed exposition and page filling (which in turn could lead to stuff like plagiarizing facts about ferrets). Of course people are still writing historical books today but yeah, it seems like the settings and history are more in the background? idk.