My mother was married three times (my father was her first) . In later years, I recall mentioning to my mother that the last two seemed a lot alike, but my father was different. Her response was most revealing about relationships.
She said that she didn't like the feeling of "helplessness" when married to my father, and liked that she felt more "in control" with the following two husbands. The last two were great guys, but they typically deferred to her ("happy wife, happy life"). My father on the other hand called the shots (and also did so with his second wife).
Personally, I'm old enough to reflect back on my many varied relationships. It always seemed like the ones that I was really into were usually the biggest headaches. Meanwhile, the ones that I was luke-warm about, seemed to require the least effort and the least headaches. Through the years, I've learned how to playdown my interest - which has been beneficial to the outcome, but still make mistakes here and there.
All and all, I think it's the same analogy to women wanting to be with a guy that gets their juices flowing... but also looking at the practicality. In other words... the "thrill' or a relationship VS that of a long-term relationship.