[Acolyte]

I think the limiting factor is the extreme rarity of celestials on Earth in canon IN that prevents constant disturbance. Sure, LA is ALWAYS going to be loud with that many demons whomping about, but you wouldn't need to get too far out of the city to escape that--just over the mountains to the North, in the desert, I imagine it would be very quiet indeed. Only major metropoli are likely to have regular disturbance.

...plot hooks aside, of course.