Chinese government is the worst in sharing and caring, that's all I can say. Why would anyone want this dual citizenship with China? The mistrust is deep. It's as old as a law 200 years ago in Qing dynasty. Chinese people are opportunists, that's one reason. Some expats just wouldn't give up the chances of reaping benefits in between China and another country: the grey zone. If there's no way back, maybe those people would give up on racketeering.
全球有160多个国家不同程度地认可双重国籍,海外华人对此呼声也很高, but 中国不搞双重国籍 - Chinese tradition: Chinese people should live and stay in 'TianChao/China', and anyone who leaves China are bad people and should get some penalty. TangSeng, JianZhen FaShi all left China illegally and lucky didn't got caught.
Talking about dual citizenship in China now is a moot point. With so many Chinese citizens desperately trying to get out of China, outside of china who in their right mind want to have Chinese citizenship?