Re: doors to quarters have no locks / crew have no expectation of priv
There are many episodes in which we see that people need a security override to get into someone's quarters without permission. More generally, we hear the door chime sounding and the occupant giving verbal permission to enter before the doors open, which can be interpreted to mean that the computer recognizes the verbal cue and unlocks the door.
If there are scenes of people just coming into quarters uninvited, that's just dramatic shorthand to get the scene moving. You can see the same thing on countless sitcoms -- nobody in sitcoms ever seems to lock their front door, because going through the business of knocking and giving permission and opening the door would throw off the comic timing so it's better just to have the wacky neighbor barge in on cue.
We hardly ever see screen doors or window screens in TV, either, even though never seen a house without window screens. And have rarely seen a house with no storm door/screen door.
Remember: No Matter Where You Go, There You Are...88
May have been the losing side. Still not convinced it was the wrong one.