The philosophy of some stores is to get it now because it may not be there tomorrow. The philosophy of Big 8 is that we have an ample supply. Wal-Mart will stock shelves a couple of times and when it's gone you're out of luck. My dad said you couldn't sell groceries on an empty shelf. They have changed nationwide.
People have a lot less time to cook.
They want to buy prepared foods. Or they use fast food restaurants instead. We still sell lard and Spam, even though people are becoming more health conscious. But tostadas made with lard still taste good. We like to introduce new items.