[qw]

The shoemakers also repaired and maintained shoes. They would replace soles, repair holes etc.

[dmurray]

That's an argument for needing fewer people, not more - since it happens in situations where it's less labour-intensive to repair shoes than to make them from scratch.

[Someone]

Not necessarily. If the materials are expensive, paying somebody to repair a shoe can be the cheaper option.

I think people still repaired socks after knitting them was automated for that reason.

The first automated knitting machine was from 1589. Queen Elizabeth I denied its inventor a patent “because of her concern for the employment security of the kingdom's many hand knitters whose livelihood might be threatened by such mechanization” (https://en.wikipedia.org/wiki/William_Lee_(inventor))

Edit: maybe not. https://www.historylink.org/File/5721 learned me that gear for us soldiers in World War One was knitted manually. Maybe, those machines weren’t used (much) yet by then?

[TheCoelacanth]

Isn't the main reason that making from scratch is less labour-intensive than repairing because of mass production?

With medieval production methods, I would bet that making from scratch is significantly more labour-intensive than repairing.