Chains of command

There is never any sneaking around in the dimly lit corridors of ship’s night, or discreet Vulcan kisses in the nooks of engineering.
Unless Jim is incredibly tired, or stressed, there are no lingering looks on the bridge, either.
The stakes are far too high.

OR

Admitting to each other that they are in love is not an issue. The problem is revealing it to everyone else.
This is how Jim and Spock’s relationship would be if Starfleet actually enforced fraternization regulations.