Some Wal*Marts carry products that other Wal*Marts don't...there are regular Wal*Marts, and then there's the SuperCenter Wal*Marts. Corporate does in fact makes the stocking decisions, as well as the individual store's Marketing Team...but there are ways to get certain products stocked on your local Wal*Mart's shelves...
BTW, Wal*Mart DOES carry Crappie Niblets...perhaps you need to peruse more closely what is on the shelf.
Roaming the banks of the Kankakee River and anywhere else fish might lurk.