Why do most everybody incorrectly assume that everybody else is 'on' facebook and/or twitter etc.?
They are a means of communication, whether you choose to receive information that way or not. The same equally applies to all opt-in forms of communication, including the Internet in general, newspapers, TV, radio... The only universal form I can think of, other than going to look at information posted at the offices personally, and that is not opt-in, is the post.
Facebook (and Twitter etc) makes it easy for information providers to distribute their information, and for interested parties to subscribe to those news feeds and be alerted to updates in real time, and the provider doesn't have the overhead of managing email distribution lists or whatever. Use it or not as you like, but if you have the capacity yet don't avail yourself of the benefits you have no cause for complaint.
The section of the population unfamiliar with Internet things (specifically the elderly, but they're catching up) that may be unreadable by these methods are not missing out as such, because the live updating is not something they would have been used to anyway.
Time will come that instead of legal announcements having to appear in The Times, they will have an Internet channel such as Facebook (or some service specifically for the task).