After what I've read on this site, is that there is a "glitch" where Sims lack some traits.
Can't say why it took so long before you could get them together Rachel. When you finally got them to marry, you should be able to see what traits the guy had. Did he have commitment issues trait? If not, it could be that he was in relationship with someone else.
I always use Get to know, ask for career and ask if single when socializing, and alot of chat of course