I think people seem to be taking a stance of "this person doesn't talk about fucking someone 24/7, guess they never want to have sex!" which is, honestly, really fucking stupid.
I mean most people don't walk around talking about how much they want to fuck a person. People can do other things and still be into a relationship. People can also not be into a relationship right now because they have something going on (like finding your father figure, saving your best friend from making a horrible mistake, trying to find a mythical object, trying to do whatever Goku does). Just because a 17 year old boy isn't like "OH MAN I CAN'T WAIT TO FUCK ALL THE TIME." doesn't mean he won't want to later on or that he won't enter into a relationship later in life (which is why OP's "but he was never interested in Hinata!" is so baffling. People hook up with people they were attracted to when they were 14 all the time.
Not everything has to be a romance. Not everything has to be overt and spelled out either. Lots of stories tell well crafted love stories without a single bit of physical contact between two people.