Because China wants to focus more on having a manned space station orbiting by 2020, China's space program reports that it does not have the finances to embark on a manned expedition to the Moon. A lunar probe is in the works.
Wang Yongzhi, who headed the last Chinese space mission which sent ex-fighter pilot Yang Liwei around the Earth in a rocket, says that it will take 15 years to get a space station completed. So far the program has been highly secretive.
The Beijing News reported the comments Wang made about this program to high school students. The US recently announced it may prevent China from participating with the international space station. This may be why China wants its own station. Source