Distinguishing between customer needs and expectations is of key importance here. Needs are those requirements that a customer has, is aware of (they are specified), and communicates to the service provider as a necessity to be fulfilled. Expectations, on the other hand, are requirements that the customer does not communicate to the seller because they are too obvious to them due to the assumed certainty of execution (probability close to 1) or they are unaware of their existence (probability close to 0), even though they are still their needs, just latent ones. Therefore, the difference between the correctness of service execution and its quality usually boils down to satisfying expectations, not just customer needs.
In 1984, Japanese TQM consultant Noriaki Kano developed a customer satisfaction model. In it, he divides the characteristics of a product (in this case, applied to a logistics service) into 3 categories, depending on the impact they have on customers. The first category consists of basic requirements (dissatisfiers), containing the fundamental elements of the service which, for obvious reasons, the customer does not articulate, assuming in advance that they are guaranteed by the service provider. These are the basic benefits for the customer, obvious to them, unspecified, and almost subconscious. The second category consists of additional requirements (satisfiers), i.e., those elements of the service that are most often associated with the desire to reduce the costs of obtaining it or to meet enriched utility needs. These additional benefits for the customer are primarily related to technical factors, and for this reason, they are specified, established, and conscious. Finally, the third category is latent requirements (delighters), containing those elements of the service that positively surprise the customer.