This is certainly a growing trend which was first started amongst end-users themselves, and slowly we've seen a few news media outlets also following suite. So far, only a very few government agencies have actually followed. Coming to mind are also The Netherlands. What is attractive for many organisations and agencies on Mastodon, is that...
The Dutch government also launched their own mastodon instance recently at social.overheid.nl. Several government departments have already joined. I hope politicians will also make the move, although I do not know if this specific instance allows for accounts other than those of government departments.
When you make public announcements as a politician or political party, it should be done via a channel that can be accessed without registration!