New announcements are historically made at the service meeting, the least attended meeting by the public (by JWs too).
Example, the updated version of the "Organized to Accomplish Our Ministry" was a special release at a service meeting with a big hoopla about a special announcement.
Also, the change in the donation arrangement was made at a service meeting.
Also, disfellowshippings and reprovings are only at the service meeting.
They don't want to scare off the "new ones."
Blondie