Because its priorities are entirely screwed up, as is clear from this article in today's Washington Post:

"In foreign countries, televisions are privately owned and you can broadcast whatever you want," Wang Weiping, deputy head of the series division at China's State Television, Film and Broadcasting Administration, told the Southern Weekend newspaper recently. "But in China, television is the mouthpiece of the party and the people. This is its main mission, and entertainment is secondary."

Imagethief thinks this is exactly backward. The first priority of Chinese television should be to entertain, because there is nothing more dangerous on this earth than 1.3 billion bored people. Bread and circuses, people. The Romans knew this 2000 years ago. (Of course, the Roman empire vanished 1500 years ago, so perhaps that's not the best example but work with me.)

After the entertaining is over, then the television can be the mouthpiece of whatever it wants. The party, the people (sounds disturbingly like public access), or even that guy who sells the harnesses that make schoolchildren stand up straight. I really don't care. But keep the party and the people out of prime time. After all, what could be better for the harmonious society than a good sitcom from time to time?