One the best scenes of Star Trek II: The Wrath of Khan was the dialog between Kirk and Spock in Spock's quarters.
Kirk was debating whether to take the training crew of the Enterprise under Spock's command to a potentially dangerous location.
This scene is so good since it shows how two totally different people, one totally logical (really utilitarian stoicism) and the other passionate, can be friends and colleagues.
If you watch the other Star Trek movies and even the original series, these two and McCoy would just hang out together.
But what's the use of hanging out? Well, friendship in and of itself has no uses per se, but is a good in itself. Natural Law Theory defines friendship as one of the basic goods that is good in and of itself.