In modern food distribution, seasonality and origin are often lost entirely from the foods Americans buy. If it’s cold where you live and you want a banana anyway, there’s nothing stopping you from having one. In that context, soft wheat flour’s stubborn regionality is almost charming. According to Phillips, biscuits likely developed as a southern staple food specifically because the flour necessary to make them was (and still is) made from the kind of wheat that’s farmed there.
Most of North America’s hard wheat is grown on the plains, from Kansas north to Canada, but because of climate differences, the South has always had the softer kind, and cooks in the late 1800s didn’t have food-service giants like Sysco trucking in mass-produced flour from thousands of miles away. As a result, biscuits are uniquely southern, and they seem determined to stay that way.