The main use of interrogative intonation is for the posing of questions. However, by comparison with declarative intonation, the interrogative pulls back from the domain of assertion, which is always more forceful than that of questions. Diminished force, for obvious reasons, is associated with politeness, to which assertiveness is always alien.
This use of interrogative intonation in the service of politesse was brought home to Y-H-B the other day while sitting in a doctor’s waiting room and hearing the first and last names of patients called out by a nurse in order to signify that their turn has come to be examined. Invariably, the full name was uttered by the nurse with interrogative intonation, not declarative. Now, this usage can naturally be understood to signify something like the unasked question, “Is So-and-So here?” But this interpretation is largely gainsaid by the fact that the patient had already registered their presence with the receptionist before taking a seat in the waiting area. This leaves politesse as the sole reason for the use of the interrogative intonation.