My former congregation has a lot of members and most go. I think it has to do with social reasons more then anything else. Plus the demographics in that congregation are all about the same. Most everyone there is poor , stupid, and a little off mentally, so it's the perfect hall for the cult. It even attracts members from outside the territory in fact I'd say half are not assigned there.
In the other hand the other congregation that shares the hall is clickish and has more of a mix of people and only around 40 people show to a meeting .