So here’s the thing about D&D: it makes no sense. None. Don’t get me wrong, I like it and all, but the world as presented is completely wrong-wrong-wrongity-wrong, and the new Pathfinder setting (much though I enjoy it) has done nothing to change that.
You wanna know why? One word: magic.
Magic in D&D is reasonably common, which is bad enough, but what’s worse is that it’s reliable. If you cast magic missile more than once, the only difference between castings is precisely how much damage you’ll do, and even that will vary only within strict limits. Which is bad enough.
Where magic gets really bad, though, is in the utility stuff. Don’t tell me that a world that has fireball lacks, say, a spell to keep food from spoiling, a spell to make a roof more weathertight, or a spell to keep bugs out. And given that even the smallest town is likely to have a person who can at least use level 1 spells, life in a D&D universe should not look much at all like the pseudo-medieval setting it generally defaults to.
I mean, consider continual flame. A magic item that can cast it at will would cost 10,800 gp and take 11 days to make; it produces items (gravel-sized stones would be great) that appear to burn but need no fuel or oxygen and never go out. And then the city that made it could have streetlights for the cost of whatever they’re mounted on, requiring no fuel or maintenance, and easily replaced if stolen. And could start exporting “flaming” stones for a little over the cost of shipping…assuming anyone could be coerced into buying them. Everyone in town could have all the light they needed, and trust me when I say that that mere fact is enough to make a lot more work and production possible.
How about teleportation circle? It costs 1000 gold to inscribe, and the circle’s only 10 feet in diameter. More to the point, you need a 17th level caster for it. But you can make it permanent, and then you have a circle big enough to drive a largish wagon into that will send your cargo to the destination instantly. I can see a wizard retiring from adventuring and going around to cities and large towns, offering them teleportation circles to other places for, say, a couple months’ worth of room and board. It’d only take a decade or two before a whole continent would have a transport network that would put the US Interstate system to shame. Pretty soon people would start doing it for destinations inside large cities, and then you don’t even have to walk through rush hour anymore.
Cure light wounds? No more crippling injuries from stupid accidents. Purify food and drink means no one gets sick from food gone off. For that matter, a 5th level cleric can feed 15 people a day with one casting of create food and water, which means famine not so much. Repel vermin, made permanent, means one can sleep without worrying about lice, mosquitos, bedbugs, or any of the other disease-carrying bugs of the world. And if you get malaria, the cleric can fix that, too, so no need for sickle-cell.
If you can summon and bind fire elementals, you can make steam engines that require no fuel. Unseen servant can do drudge work like cleaning or weaving, freeing up humans to do creative things. With a decanter of endless water, deserts can be easily made fertile; with a bottle of air, mining is no longer such a dangerous job…assuming you actually mine, instead of getting your iron from the wall of iron spell. Anyway, just get a druid to stone shape the shafts.
Sure, people might not think of all these things immediately, but it wouldn’t take long; we monkeys are always looking for ways to do less work. And a magic-driven world would be cleaner and safer than a technology-driven one, because magic doesn’t produce waste.