Because you don’t know what the one item a customer HAS to have is. I told the GM of my grocery store that because he did not carry Apple Store gift cards on his rack he was losing at least 2 trips a month from me. I don’t let myself have more than I budget for my game, I don’t want to use a credit or debit card for it. So every time I wanted to buy that gift card he was losing the whole sale to a store that DID carry them.

They appeared on the rack a week later.