These exchanges very likely have high ranked government officials in their board, which grants them the freedom to do as they please.
Back in the days when they were leading with millions of Bitcoins in daily trading volumes they almost terminated every retail trader by not only front running their orders, which is what high frequency traders depend on and are willing to pay big money for, but playing with the market in such a way that retailers will end up losing on the majority of their trades due to the manipulation. How can it be that these exchanges have never been punished for that? It's only possible when authorative figures close their eyes on purposely.
Any other exchange, especially in China, would have been raided and wiped out already.
No doubt administrative organization interferes the marketplace. As long as I know, FBI holds 160,000 pieces bitcoin, and Chinese government obviously gets NEO's (Litecoin seemly) back. One point I think you missed is that many foreign traders are not covered by the law which the exchanges are.