Plus, aboard a starship, everybody knows everybody anyway (although in TOS it was a bit easier than in nuMovies, considering the crew size difference!).
The TOS crew was still over 400, do you really think that everybody knew evedybody, including their ranks? The company I work for has about 150 employees, and I'm one of the few people who really knows everyone. Normally, people from let's say the development department have no idea who works in the accounting department and vice versa. Add the personell rotation rate of a starhip to that!