I think people exaggerate the goal of the "Points of Light" setting. The goal is not a Monster Apocalypse, with a horde surrounding every settlement. The goal is uncertainty.
Yes, you know there's a village up on top of that mountain. The last time anyone from your village went up there to trade, it was your father before you were born, and he lost his brother on the slopes to frostbite. If the monks are still there, maybe they can guide you to the Temple of the Wind God. Maybe they've become degenerate cannibals. Maybe they're all long dead and their bones will rise up to beg you to seek vengeance for them the moment you step into their land. Who knows?
The point of the PoL setting is that people don't
know about what lurks in the darkness at night, or what is beyond the horizon. Major cities might have maps compiled by traders and explorers, but they won't be accurate or up to date except for the most frequently traveled routes and destinations. There'll be misinformation and legends about the people, places and things that lurk beyond a village or a city. "Them folks across the mountains- they heads are backwards and they do everything in reverse!"
In your standard D&D setting, the feel is very modern- there aren't a lot of blank spots on the map. Eberron is closer to the 1930s in 'feel' than it is to say, the world of Robert E. Howard's Conan.
I don't get the impression it's like a Zombie Apocalypse, with settlements constantly struggling for survival against a horde of monsters. My impression is that settlements are routinely struggling for survival against the elements, and perhaps once a decade or twice a generation faced with some challenge (monsters, raiders, etc) that threatens their survival. Which is not to say they don't get raided or monster attacked, but that these are limited in scope. The gnoll band hits one farm and moves on rather than heading for a clean sweep, either because they want to get away before alarm can be sounded or that they want there to be a community in the same place next summer and if they kill too many, the place will die out during the winter.
The Pol may not have the larger organized state but all the other ones can easily be there.
Plus, places can be protected unintentionally. Say Village A is located next to some difficult terrain, and on the other side is far wealthier Village B. Raiders hit B and, satiated, never get around to hitting A, which while not nearly as well off as B during good times, is essentially shielded by its existence.
Likewise, take one of the city-states at the entrance to a mountain valley. The villages down the valley enjoy its presence blocking an entrance into their region.
How a settlement survives is a great question to ask when designing and building settlements, and there are thousands of possible reasons, all good for gaming. ("Yearly sacrifice to the Dragon...", for instance, is a great one. You just need an uptight British policeman to investigate a disappearance)