pawsplay
Hero
Just by the RAW, if you keep most towns under 5000 people, there is not a lot of magic floating around. In my current campaign, my players keep stumbling up against the "GP limit" and the levels of NPC spellcasters when they go shopping. I don't go for "no scrying," but at the same time, I don't want to rip out huge amounts of the rules.
So most experienced NPCs are under level 10, most towns are 5000 people or less, the kingdom's capital is 50,000, planar portals are rare, most communities are mono-racial, etc.
The PCs, by contrast, are armed to the teeth, can stare down most "ordinary" threats, whether the master knight or a gang of ogres, and can acquire more phat loot only by slaying dragons, looting cursed tombs, traveling the planes, visiting the town around the tower of magic, etc.
So most experienced NPCs are under level 10, most towns are 5000 people or less, the kingdom's capital is 50,000, planar portals are rare, most communities are mono-racial, etc.
The PCs, by contrast, are armed to the teeth, can stare down most "ordinary" threats, whether the master knight or a gang of ogres, and can acquire more phat loot only by slaying dragons, looting cursed tombs, traveling the planes, visiting the town around the tower of magic, etc.