Why is there no extradition treaty between China and the United States?

It used to be a joke that China did not sign the International Covenant on Political Rights at the United Nations. As early as 1998 10, the Permanent Representative of China to the United Nations, Qin, signed the International Covenant on Civil and Political Rights on behalf of the government of China at the United Nations Headquarters. When Obama was in office, the US Congress didn't want to pretend to be B. In fact, there were great differences on the proportion of returned funds involved by corrupt criminals, and the United States did not agree to deal with it according to international practice. Every year, the card is here every year.