Many JWS do this invite for the memorial as a means to reconfirm their own self righteous value toward themselves.
They haven't been going out in service much so they feel a bit guilty about that so now they are taking the opportunity by showing their steadfast devotion to their god who watches and evaluates their devotion, which in reality is conducted by the heads of the congregation the elders. which the Watchtower Corporation has purposely devised.
The invite to the memorial takes a bit of pressure off of what the WTS heads impose to proselytize the faith and JWS are continuously pressured to do so..
The pretentious hubris of religoius devotion is is a constant observation with JWS, which reflectively isn't surprising given the amount of guilt and pressure to preach and draw in more people to the flock so to speak.