C.E. Evans wrote:
What Starfleet did was loosely model itself after Earth's oceangoing navies and some other organizations, but not everything is the same. Being an organization from another time and place, you'd actually expect some differences here and there, really (even if it's only in the way they commonly address their personnel).
Although I don't think that the structure of a police force really gets to a solid explanation about how individuals off all ranks in Starfleet can be named, it does at least illustrate that there exists a myriad of structures to emulate, depending on the organization's needs. (Enlisted) Crewmen work very closely with commissioned officer in Trek, and probably have a high degree of personal responsibility. The common demonym ought to reflect that.