My prior understanding was that before the industrial revolution dramatically reduced the labor costs, clothing was expensive. Most people only owned two or three outfits, and replacing one would cost a month's wages sort of expensive.
How could one afford to throw away a perfectly good non-matching shoe?
they threw away the broken one after replacing it with a new one. they didn't replace the good one.
when shoes are hand made it makes sense to not make them only in pairs if only one shoe is needed