For the government the answer is clear: locally situated companies that they have total control over. WeChat will obviously never pull a Google style "encrypt all the things" - they'll happily help the state reduce the credit scores of political dissidents and anyone who is friends with them.
For politically connected cronies (e.g. WeChat owners), the answer is also clear.
But if you are just a Chinese citizen, what do you gain? Inferior substitutes for the Google/Facebook/etc infrastructure? Isolation from the rest of the world?
[1] This excellent article argues that WeChat's "conversational interface" is just a crude hack around app store restrictions. http://dangrover.com/blog/2016/04/20/bots-wont-replace-apps....