If you like a person but the sex is bad, do you spend time trying to work on it, or do you bail? What do you say to the person? “I don’t think we’re sexually compatible” seems to invite the whole “let’s try to work on it” discussion.
Personally, if the sex isn’t there I’m out. For me, there are far too many things to work on in a relationship, and having to “work” on sex seems like a lose/lose proposition—especially when I’m fully aware that there are plenty of women out there with whom I wouldn’t have to work on it at all. (Now, to be honest, in my case, I’m a guy with intimacy issues who has to imagine myself strangling a drifter in order to climax during sex, so take my words with a grain of salt.) But the old saying “Once the sex goes, it all goes” kind of applies. What do you think happens if the sex was never there to begin with? On the other hand, there are plenty of people who have had success in the bedroom after working toward a mutual goal through time, work, and communication. I just don’t happen to know anything about that.