![](http://4.bp.blogspot.com/_L7F0Sur_AOo/TNtdJvEwaII/AAAAAAAAAAo/4wwqOYZsk9o/s400/child%2Bslave.jpg)
Mainly because children serving as killers is really going on in the world. Whereas nobody really flies on brooms and vampires don't really exist. And then there's a portrayal of a dystopian future and the chasm between class distinctions being highlighted. But, hey - you'll probably say I'm full of s_it, and there's no difference.