A couple thoughts occur:
- If you wanted to justify big cities in wildernesses, you could use the prevalence of monsters to do so. Say it’s just too dangerous to have small villages, and everyone has to spend the night in a walled town/city for their own safety.
- I’m pondering how magic could effect this, too. You might have a whole Town in this ecosystem replaced by just a single wizard, who’s willing to magic up complex tools or luxuries in exchange for an exorbitant payment from the peasants.
- A lot of fantasy settings are lowkey post-apocalyptic, inspired by the Dark Ages and/or The Black Death. You may encounter isolated Villages that are struggling to scrape by as their Town got wiped off the map, or isolated Cities crammed full of starving refugees that fled their Villages.




For sure! And that scarcity of resources and failing supply chains is a GREAT setting for questing!