Probably because the latter half of your assertion, that "Facebook turns over the information you provide to whatever government entity you are hiding from" is a lie. This protects people who feel they need to hide the fact that they are connecting to Facebook from an observer/ISP.
Maybe my phrasing was overly strong. As I understand it, there are no guarantees that the information that we put into a service like Facebook can be kept out of the government's hands. Whether or not Facebook is doing it willingly, is not relevant to my question.
What is the value in using tor to connect anonymously to a system that ties back to your real life identity?
The tie is only temporal, and it's still anonymized.
The only concession is that now the government you're avoiding might know you use Tor, if Facebook tells them.
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Here's the usage case: you're a foreign national visiting a country with a restrictive firewall, like China's. Now you can continue to communicate with people back home.
Facebook already had your information, in this scenario, so nothing has changed except that they know people from China are desperate for their services. That's only good, in my book.
