Not the average foot size?
The average women’s shoe size is a 7 or 8 which means that when stores order a shipment of shoes they order more in those sizes. I personally have small feet (5 1/2) and while I can sometimes get away with wearing a 6 it doesn’t always work, especially when it comes to flats and pumps. And then there’s the problem of fighting over the two pairs of size 6 sitting next to five boxes of size 7 on the shelf.
The other day I was pleasantly surprised to see that Aldo shoes has a “Special Sizes” section on their website. Currently there are only size 5 and size 11 options but that’s an improvement from designers who completely ignore the small/big footed minority.