I'd sure love to see the documentation to support the idea that shoes weren't sold in pairs. That's about a fine of a tale as Washington's cherry tree. Lachet shoes were still popular into the early 19th c. James Monroe sure liked the older style as did Madison. I've never seen a likeness of John Marshall wearing a buckled shoe, but Jefferson had both. While the French revolution did effect fashion taste, as you can see in any public place, it's not universal.