Yeah, but they do act immaturely around diplomats, ambassadors, etc. For example, in "30 Days" Paris is out of line when he accuses the water world aliens of destroying the ecosystem during a meeting on Voyager. We may sympathize with his beliefs, but as a junior officer he should keep his mouth shut and express his reservations to Janeway privately. Acting as he does, he embarrasses Janeway and only makes the aliens mad.
The whole point of the ep. was about how Tom took his privileges too far. The result was him being reprimanded and demoted.
So they showed us first hand what happens when an officers immaturity crosses the proper boundries.
How mature was Data upon meeting the ambassibor/captain in "Starship Mine"?? He was basically making fun of the man to his face................and Riker, Troi & LaForge were all laughing at it. These vacation on Riza for crying out loud.
Even the stuffiest of shirts got immature and let their freak flag fly during their personal time.
Before "Distant Voices", how mature was Bashir?
Remember how stupidly insulting he used to be on and off duty?