Really because many government organizations have taken to twitter/social media to be the official (and in some cases only) method of public alerting and notifications around emergencies, school closing, traffic alerts, and a wide range other topics.

So if I am not allowed to access twitter, or banned from the platform then I am being banned from participating in my local government

So if it not a public service, then public organizations (like police, fire, schools, etc) should be barred from using the service