Farscape had a smaller cast than most Trek shows, though what made John and Aeryn work more than anything was the chemistry Ben and Claudia had. Because their characters...didn't have a lot in common to lead to a relationship aside from them both looking human.
Even then the show had some difficulty justifying why the crew stayed together.
For the life of me I always wondered why they bothered keeping Rygel around. Or Jool. Or Chiana or Noranti.
They were all outcasts from their respective homes, except for John who was a stranger in a strange land (and hunted by Crais for a time). Better to stick together for common defense than to take off on their own. None of them can go home again and they have a leviathan to provide a place to live and for defense.
But what did Rygel or Jool or Noranti contribute to the crew? They caused more trouble than anything else.
Comedy.

In all seriousness, Rygel was their negotiator at times, along with John, and sometimes Zhaan. Rygel managed to get the Pirates for one episode, food very commonly, among other things.
Noranti cooked and that alone meant Rygel would fight to keep her. Jool is more a mystery, but so what? The ship was on the run from Peacekeepers and other baddies, and you're going to stop and ask what you've done lately?
Like JD said, it's not really a crew in the traditional sense, but a band of refugees who are brought together by circumstance. Like Lost.