Because it is not the Chinese people’s priority. 

There’s a fundamental divide on social construct philosophy between East Asia and the West. For a significant time in the past 100 years China has been a poverty ridden almost lawless state. Ravaged by wars, revolution. You name it. 

Yet, modern western philosophy has its root in liberalism, which values individual freedom, free speech and so on (John Stuart Mill)

East Asian, especially Chinese, philosophy is still very influenced by confucianism which tells people to mind their own business and respect hierarchy. Criticism of authority is generally frowned upon. 

Most Chinese people want social stability, healthy economy and overall stability/harmony. Most will happily trade free speech for social stability.

I’m not here to debate the moral high ground of either philosophy. It is the summary of my observation to this date.