I think Aikido attracts people interested in self-defense that has a less "fighting" aspect to it.
my head just wrapped around the pole on that one. i noticed that as well that many folks who came to our dojo mentioned about learning self-defense but the hate the idea of fighting. most of them, as uke, their attacks were terrible, i.e. bad in form and content. then i would spent time teaching them about attack which made them feel kinda uncomfortable because it felt like fighting. then i would spent time explain the uke-nage model where if uke doesn't perform his/her/it job to the fullest, then nage can't perform his/her/it job to the fullest, then we would just have crappy aikido.
in general, i see that aikido tends to attract the passive-aggressive folks.