People on the team who like to have presence on social media do that. People who don't like it that much, don't. I don't see much politics in this but maybe I'm missing something.
It's an interesting day when Github issues on an official project are considered "social media". I think that can be taken many ways and most of them interesting to ponder.
Yes, but then again, the whole selling point of Github is that it's social media attached to git repositories. That's the reason it's the open source code dumping ground.