They're not posting to Facebook because they need to. From the article:

The silver lining here is that Facebook was already increasingly a waste of our time. The only reason we’re able to share our stories via our official Facebook page is that we’ve fully automated that process, because it is not actually worth our time to post our stories there organically. Since before we started 404 Media, we knew there was very little chance that Facebook would help us reach people, grow our audience, and make the case that people should support our journalism, so in a way we lost nothing because there’s nothing to lose.