There is always that girl who gives other girls a bad name. She likes the "challenge" of a guy who is taken. That isn't always the case.

I have noticed this trend when I am in a relationship. I believe it is at least partly because people who aren't "looking" for a relationship/to get laid/for their soul mate, tend to be more at ease. This can create a facade of confidence. This can be attractive. People can smell someone who is "hunting" a mile away. This can come off as creepy, or just desperate. It isn't attractive sometimes (There are always the people who like desperation in a prospective mate).