I think its because that's what the media and non-art people focus on both in and out of China. Its easier to understand than zodiac heads which has lots of historical backstory and questions what is traditional.

But of course he is milking it. (after all the exhibit is called "Evidence")

aesthetically I'm much more impressed by this guy: http://www.caiguoqiang.com/projects/inopportune-stage-two-20...

but you could accuse him of being decorative and of using stereotypical Chinese imagery. I still like it.