Because they think about Hiei and Kurama? Or are you saying that you think people think Hiei and Kurama annoy you?
Anyway, this thread is hardly 80% "I WANT PINCH HIEIS CARTOON ASS". There's a lot of talk over Kurama's bod, too.
Seriously, though. Questions like "what would they say" about this or that are purely conjectural based on the personalities the author has given them and assume that the reader will add the obvious "if they were real" sentence fragment. Comments like yours only serve to annoy others and prompt flaming.
Sure we fangirls are crushing on imaginary characters. I like to think that most of us realize that they're imaginary and there's no way that any of us will ever be able to really date them.
In fact, that's kinda the point. Real guys can be a real bummer sometimes. (Says the girl who's never been on a real date.)
Fictional characters are 100% safe. No worries about regection, STDs, or whathaveyou.
Not to mention make for much more fun, silly, and diverse conversation. (Like I'd really be able to get into a conversation about some real life guy I've never met and know nothing about.)