There are ISPs allowed by Gov to provide uncensored internet access, those are unblocked.

Otherwise personal use of VPN can be blocked by the gov. See for example: https://news.ycombinator.com/item?id=5357590

See also the top comment of this: https://news.ycombinator.com/item?id=10101469

I've read (in Hacker News comments from developers in China) that international corporations get specially-licensed dedicated connections in China that don't go through the Great Firewall at all. So any VPN use on a connection like that would be for security, not to defeat the censors.