Final answer:
Services are variable because service quality depends on who provides them, as well as when, where, and how they are provided.
Step-by-step explanation:
The main reason for services being variable is that service quality depends on who provides them, as well as when, where, and how they are provided. Services are intangible and cannot be separated from their providers, which means that the quality of service can vary depending on the skills and abilities of the service provider. For example, the experience and expertise of a hair stylist will determine the quality of a haircut, or the efficiency and accuracy of a bank teller will determine the quality of banking services.