Fridge Logic: The world they live on is violently seismically active; Damien observes in the first book that the only thing that keeps the city standing through the violent quake is the quake-wards. Now that the fae is unusable by humans, aren't earthquakes going to destroy them all?
He's also shocked to see the quake-wards for the first time at the beginning of book one, though; people of his native region had done well enough without them. Presumably they'll have to build shorter cities now. (Also keep in mind that the fae is NOT unusable. Just...pricey. There will probably be a few willing to pay the price to protect the really important places.)
Not to mention that the Cathedral didn't even need Quake Wards due to the strong faith of the church's adherents subconsiously shaping the fae. Presumably if you combine that effect with the more advanced technology now able to be used you can get a workaround.