One other thing I meant to mention before is the whole "I want to be loved" thing that seems to be behind a lot of shipping. It seems, though, that it comes from two directions: "I want to see the love, even if I can't have it myself" and "I don't want someone else to have all of that love." The second ties into the whole male benefits more/female acknowledges weaknesses/etc. stuff. Somebody not perfect gets the love and devotion that you long for, and you don't like that. One of the explanations I've seen for slash is that slash fans seem to identify more with male characters than female, so they slash the one they identify with with the one they find hot(often also the one prone to expressions of love, conventional or otherwise.)