The local supermarkets all stock literally one or two boxes on the shelf at a time, even though I know they have more in the back because as soon as I buy one it's put back on the shelf the next day. Something really funny is going on, I wouldn't be surprised if they had some contractual arrangement to artificially limit the amount that appeared in stock, to make it seem less appealing.
As someone who has worked in a grocery store I think you're reading way too much into it. They have priorities when stocking shelves but I think conspiracies by Big Detergent to get you to buy tide pods are low on the list.