Something I've never been able to puzzle out an in-universe reason for....
In the course of the episode "The Tholian Web," Capt. Kirk disappears in an 'interphase' event, along with the ill-fated USS Defiant. He is ultimately declared dead, they hold his memorial service, and Spock and McCoy watch the recording he'd left of his last orders and advice to them.
Ultimately of course, Kirk is found and rescued. At the end of the episode, he tells Spock and McCoy he hopes his last taped orders were helpful to them through the crisis. But Spock and McCoy lie and say that they were so busy, they never had the chance to watch the tape.
OK, so out-of-universe, it offers the audience a chuckle. Kirk's confident assurance that his taped last orders were something moving, significant, helpful, etc. is skewered by the offhanded dismissive response, "Oh, yeah, that... naahh, didn't have time, it didn't seem important."
But in-universe, why would Spock and McCoy want to mislead Kirk and make him think they never watched the tape?