Why would you drive into the medieval centre of a city to do a large supermarket shop if you can drive to an out-of-town one already?

Studies show that - particularly in Europe - most people are already walking to these shops everywhere. The 'weekly shop' is not really a thing that inner-city dwellers tend to do that often - they either rely on deliveries (cheap and efficient due to density) or smaller shops throughout the week (which often means less perishables waste.)