I assume 1) people walked a lot more, 2) shoes took longer to make, and 3) didn't last as long which means more people necessary to handle demand. I could be completely off, though.
Point 3 is the key one - soles, especially. Rubber soles weren't a thing - they were made of leather (or sometimes textiles) and they wore out in a matter of a couple months or even a few weeks with heavy usage, especially give point 1.
Point 2 isn't really the case - your later period and fancier pointed-toe, lace-and-ribbon-bedecked shoes for the higher classes took probably some time, but a pair of common leather turn-shoes can be made in a couple hours.
Exactly, walking! Something few of us do these days even at short distances. I prefer shoes that can recobbled but I know from the dwindling numbers of cobblers that I'm a shrinking demographic.
