How does the service request management practice achieve its purpose of supporting the agreed quality of a service?

The official purpose of the service request management practice is to support the agreed quality of a service by handling all pre-defined, user-initiated service requests in an effective and user-friendly manner. A service request is defined as a request from a user or a user’s authorized representative that initiates a service action which has been agreed as a normal part of service delivery. Therefore, effectively handling these queries and their associated actions is the direct mechanism by which the practice achieves its purpose.

A. By reducing the costs associated with request handling and fulfilment: Cost reduction is a potential benefit or outcome of an efficient practice, not its primary purpose in supporting service quality.
B. By setting realistic expectations relating to the fulfilment of requests: Setting expectations is an important component of the practice, but the core purpose is the actual handling and fulfilment of the agreed actions.
C. By improving the reputation of the service providing organization: An improved reputation is a positive consequence of fulfilling the purpose well, not the purpose itself.

AXELOS. (2020). ITIL® 4 Practice Guide: Service Request Management. Section 2.1, "Purpose and description." This section explicitly states the purpose of the practice.

AXELOS. (2019). ITIL® 4 Foundation, ITIL 4 Edition. TSO (The Stationery Office). Section 5.2.12, "Service request management," defines the practice's purpose.