They were slow to adopt social media in the first place and needed overwhelming proof of its value before they did. Massively overhauling their social media strategy now to pivot away from Twitter/Facebook would require a similarly huge effort from public servants who are even aware of the issue.

Realistically, it's inertia. The social media "box" is considered ticked. Reopening a closed issue like that would require overwhelming proof of the neccessity of doing so.