Some of these entities - schools and utilities, I'd say - can't assume that those they serve all have internet access, so relying only on Twitter or Facebook isn't enough. My local school system, for example, issues important announcements by those means (so I hear - I'm not on either system), but also recorded voice calls and texts, to ensure the message gets out somehow.

If they post information only on Twitter ... well, it's not that important. I bet some of us lose perspective on the relative importance of messages when they are coming in from all directions.