Master/slave incorporates the definition of a supplicant subordinate relationship which is not appropriate for the context it is frequently used in. People just

Master/slave incorporates the definition of a supplicant subordinate relationship which is not appropriate for the context it is frequently used in. People just use it "because it's there". Boss/Worker, Leader/follower, coordinator/actuator and sender/receiver are all more suitable terms in the areas where they are used. None of them imply that one subsystem owns another or must be unquestionably obedient - in a system this kind of relationship is rare.