Kujhak is the only safe city for a hundred miles. Maybe more. Maybe even in the whole world. We don't get news from far off to often, so it's hard to tell. At any rate, it's the safest place near anywhere that matters.
The Gamma Knights keep it safe. They patrol the roads, they collect odd bits of lore and almost lost technology, they guard the secret places where dark things dwell in the night. They alone can turn back creatures infected with radiation, and the more powerful among them know ancient lore of healing and light, carried through the generations from the great cities of our ancestors. They keep to the old vows, too, wielding just blunt weapons and ray guns, as the ancient laws decree.
But they can't be everywhere. Outside Kujhak, off the roads, below the vaults, isn't safe. Even other towns, even places where the Knights have made treaties, it's best to watch your back, because those places may have new leaders with new ideas, who haven't heard of the Gamma Knights or at least don't fear them. The Knights would like to tame those places, but they don't have the strength or the time. At most, they can dispatch a few of their younger, rasher members out to do a bit of mapping and "creative diplomacy."