I always felt like "The Memorial" was a sort of slang term for insiders.
You would think the number of these invitations distributed in comparison to the number who attend would snap some of the stastically minded dubs to attention. You're looking at 5-10K invitations per congregation (the publishers get 50 each, pioneers get all they want) and they're thrilled when a handful total new people show up. That's a statistically HORRIBLE way to advertise. They could run a TV ad at 3am and get better results, if attendance for new people is actually the goal.
But it isn't.
It is an ad campaign but it is a "look at us!" ad campaign. Whether anything comes of it is of no consequence.
In addition it is a way to control the 'belongings' by putting them all together in an organized group activity.