It might just be the way I interpret it, but I'm seeing "nice" here as actually meaning "charismatic", and charisma in men is something that women are known to be attracted to. I imagine that many of the men here who talk about not being able to be in relationships are really nice people in real life just as well, yet that doesn't seem to make their love life any more easier. On the other hand, I don't think they're charismatic people (sorry, guys). I'm myself not a charismatic person either, yet I try to be nice... for the most part. Also, on an unrelated note, it should be noted that charismatic people, while seeming warm and inviting at first, are not uncommonly totally different people beneath the façade. To sum it up, niceness might be attractive, but I don't think it is without charisma. Not at all.