Scarcity is humanity's great motivator. This has been true forever, since back when we were basically apes: The most important resources-food, shelter, mates-were the ones that were most in demand. Shortage meant value, and being attuned to value meant staying alive. We learned to focus on the rare thing at the expense of what was around it-psychologists call this "tunneling"-and to prioritize avoiding loss over gaining rewards.
They're called Aldi Finds, though loyal shoppers call that specific aisle "the aisle of shame" because of how irresistible the novelty of those items can be. What makes them even more compelling is that returning favorites that haven't been available in several months or a full year are also frequently featured. Every now and then, an Aldi Find is such a big hit with the customer base that it actually becomes part of the permanent selection.