One nice thing about having the ceiling furred down it allows you to fish wires across the ceiling without having to cut a bunch of holes in the ceiling when going across the joists. It is pretty uncommon here, but apparently in New England (This Old House, I'm looking at you) it is common. I'd love to add some can lights in my living room (now an office) but I really don't want to carve a bunch of extra holes in the ceiling. It is on the first floor of a two-story house so going above isn't an option. If I had furring strips I could do it with just the holes for the cans and be able to go either direction in the ceiling with my wires.