Depends. Was Sisko gay? Yes, he got married and his wife was died in the pilot. Nonetheless, he seldom actively chased women. If anything, Jake introduced Kassidy to him. And Janeway hardly got any
action on her ship. And even then, this was with a hologram lol... Archer didn't have a relationship as such, just a brief fling with the CO of his sister ship.
If anything, this at least represents real life, in that there are many who don't actively seek relationships, have careers that interest them, children to raise, etc.