IMHO, I believe that the lack of participation in roll calls is for a couple of reasons:
There's way too much negativity on the roll calls that I've been on...
As a previous poster noted, not everyone has returned to cruising....
Since most lines no longer are hosting M&G's, there's less interest in getting active/involved.
Again, this is just my opinion but we've cruised 5 times since the restart and participation in all of the relevant roll calls has been tepid at best.