In all the years of handing out memorial invitations, I can think of zero people that ever just showed up off the street because of the invite. The other people attending were always family members of JWs or inactive ones.
As with all "new" forms of activity, it is for the purpose of keeping those IN occupied and distracted...NOT about those outside....
I'd love to see the data. I suspect if you looked at a bar chart of memorial attendance over the last 30 years, I suspect you'd see ZERO impact on that chart since the invitation work started.