There has to be widespread industrial magic in order to ignore its effect. Until 3E, the RAW rather discouraged widespread industrial magic due to hoop-jumping. Since we have discussed in the past the difficulties of item creation pre-3E, I feel certain you'd agree that this sort of thing wouldn't have cropped up under the magical "rules" of those worlds.
Before I get to the quote, let me say that I do agree with most of what RC is saying. And you have no idea how much that bewilders me to say.
There are two issues here though. I wasn't really talking about the existence of magic items and the creations of magic items. The simple cost of such makes them out of reach for the majority of the people. It takes a fairly significant town to get a 9000 gp Decanter of Endless Water, and by that time, it's effects aren't all that great anyway. There are simply too many people.
There is another issue though. The existence of permanent spells at low level. Continual Light/Flame, Animate Dead, Make Whole (in 3e, I used Summon Monster spells to keep bringing in Formian Workers to cast multiple Make Whole spells to repair a small castle for free - a hole that was plugged in 3.5), Bless Water, Soften Earth or Stone, healing of all forms, and I'm sure there are others, are all very low level spells, quite possibly available in fairly small settlements.
These spells all have the ability to change a setting greatly. Since they are cast by low level characters, control issues aren't really a problem. A third level wizard or cleric isn't all that powerful. These spells also existed in previous incarnations of the game, but their effects were largely ignored. At least current design philosophy seems to be taking these somewhat into account.
Of course, this is also ignoring things like animal husbandry. With the huge number of potentially extremely useful creatures out there, it's a little surprising that we don't see more of this. Hippogriff cavalry for example. Or even just using hippogriff in a similar way to WWI airplanes - spotting and messengers. I could see this sort of thing morphing into a sort of Air Cavalry usage similar to modern helicopter units. Troop transport for small numbers of troops and supplies.
The mind boggles.