Different quizmasters have different interests. However, there are a few things that a large number of quizmasters are interested in, and these form a dominant portion of most quizzes. There is some sort of a self-reinforcing positive feedback loop at play here.
And if you don’t share these “special interests”, then your average performance automatically gets capped.
Of course, this doesn’t apply in case you force yourself to develop new interests just for the sake of quizzing, but that, I think, defeats the whole purpose.