But not everyone's career path is headed toward admiral either. The higher the rank, the fewer openings there are for it. Most people in the Navy never get anywhere near captain's or admiral's rank. They retire as commanders or lieutenants or ensigns or chief petty officers or whatever they level out at. Star Trek has created an unrealistic expectation that every character has the potential to become an admiral. Which is about as plausible as an entire command crew getting to stay together on the same ship for 20 years, or to get reunited on a namesake ship after they wreck the first one.