Is there a national shortage of poop that I'm not aware of? A poop
embargo of some foreign country that gives us more crap than anybody
else?

In places that have cattle on pasture and dung beetles availability of
manure is seasonal. In the summer the beetles will destroy each pat in an
matter of days and so picking them up is difficult and hardly worth the
trouble. Turd harvesting is therefore restricted to the winter. I have no
idea if you have dung beetles in your area. In areas where cattle are in
feedlots this would not apply.

David