Kirk and Spock are hiding their relationship in plain sight. The reason why they are hiding in a 1960’s TV show is because you can’t be obvious in a 1960’s TV show, but why might they be hiding in the 2200s?

For the same reason that Spock didn’t broadcast the fact that he was Ambassador Sarek’s son: because Spock and Kirk are highly visible military men, meaning they are highly visible military targets. The less people in general know about their relationships, then the less likely it is that that info could be used against them or their loved ones by enemies. Get it?

Kirk and Spock don’t act like they are hiding their relationship from their comrades. They are discreet, that is all. Still, the very deep intimacy they share and great fond regard they have for each other couldn’t be plainer, and it certainly is beyond what ordinary good friends enjoy. It’s also fairly plain that their closest friends and comrades know what’s going on, and accept it.

The indisputable truth is this: Kirk and Spock’s relationship with each other is their primary relationship. It goes on for decades and withstands all manner of crushing trials. Even death doesn’t keep them apart. That’s verifiable canon. Nobody can convincingly deny that. That Kirk and Spock love each other more than they love anybody else is utterly obvious. That is not imaginary, nor accidental. That was intentionally placed in the show by the show’s creators, and it was in fact spotlighted in nearly every TOS story, and in the movies, too.

Kirk and Spock love each other, and that is no minor point: their unusual love for each other is a large part of what makes Star Trek unique. In fact, their relationship - and the way their relationship is respected by others - symbolizes what Star Trek is all about.