I wonder what the stats on that are. I can only think of a hand full of US metro locations that would actually have areas that I would think of as exurbs and most of them are on the coasts (sans Chicago and maybe Dallas/Fort Worth).

Since I'm not a researcher I can really only speak to my experience around Milwaukee. Basically any town within Milwaukee County doesn't (as a rule, there are exceptions) have that kind of space. But further than that, there's quite a bit of space. Probably still not fire-engine-storage space, but at least riding-mower-recommended space.