Wal-Mart was also a pioneer in just in time delivery for retail. If your supply chain is reliable you don't need to pile merchandise as high in your stores and your warehouses. People will drive an hour to Wal-Mart(s) in the most rural locations and in that case it is a real bummer to be out of stock.

I'd contrast that to K-Mart where I went to get 3 digits for my mailbox and could only get 2 of them so I didn't buy any.