I think the biggest reason is that they don't want to. But also, I don't see how that could work right now.

You can't just abolish money, the state, and class by a "push of the button," especially in a huge country like China, which has gigantic enemies that could take advantage of their lack of a strong state and destroy the whole thing.

In my mind, communism can't happen while forces like the U.S. exist on the global stage.