Because they don't want anyone to know that everything is not perfect in red China. It never rains or floods. No landslides or cyclones. Drought? That is a foreign media concoction. There is no traffic problem or pollution in Beijing either. Earthquakes do not happen and no one looks at evil western pornography on the internet.
It is difficult to get the truth there. Period. And the PLAAF DO control everything that happens in the sky.
Try not to shout at ATC because they have their proverbial hands tied. Just go with the flow or you'll blow a gasket.