There's a single DS9 episode[0] where they reveal that the Captain can actually spy on everyone on the ship at once. Like tap into a video feed and listen to conversations. But then we never see this happen again.

My headcannon for this is that even though it's technically possible, it's so unethical they just choose to never do it.

[0] https://memory-alpha.fandom.com/wiki/Valiant_(episode)#:~:te...