Since most businesses already refer to incoterms when they do cross border trade, they also include them by default when doing city-to-city local deliveries.
This is perfectly fine in most cases, however both buyer and seller must be clear on their costs and obligations. Incoterms have become an essential part of daily language of trade. They are the authoritative rule for determining how costs and risks are allocated to parties involved in a transaction.
They are often incorporated in contracts of deliveries of goods and services world-wide providing guidance to transporters, insurers, importers and exporters including international students.