"Tor provides a gateway to the free Internet, bypassing most mediums of censorship that may be imposed by someone, like for example oppressive regimes."

People sure seem to believe that getting around censorship is one of the main goals, though.

Tor does have private bridges into the network that you can request access to, which is their solution to this issue.

It's not a matter of hiding the fact that you're using Tor, it's a matter of whether it bypasses censors or not. There's a big difference between those two. Even if a censor is able to detect that an individual node is running Tor, that doesn't mean they can globally detect all nodes and then block them.

Tor's user numbers in China in particular are very low simply because it's just straight blocked. Private bridges and pluggable transports can get around that, but they're just not used at scale because that's just too challenging for ordinary users.