Enough for them to believe that they live in a democracy, it seems (and I don't say that sarcastically).

It's not like people in liberal democracies have more influence. We can't choose who runs, and each individual's vote is negligible. I don't know the specifics of China's government, but I suspect they value being able to influence local policy and higher official elections via the Communist Party more than a direct vote on its leader -- I would too, honestly.