Even as a non-believer, I still absolutely adore the Amy Farrah Fowler quote from her first appearance on The Big Bang Theory: "I don't object to the concept of a deity, but I'm baffled by the notion of one that takes attendance." Attendance was always one of the things that baffled me about Sunday mass. How could it be a sin - regardless of venial vs. mortal - to not show up in a building to pledge your undying faith? What about the people in the world who had no such buildings? Even as a young kid, I knew that to be the case in many places. This was NOT a popular subject in catechism class, as I discovered.
It is a numbers game. Look around and you will see most things are about numbers. The reason some religions (Catholics, Mormons) have large families (I was also Catholic and there were 7 kids) is about numbers. A huge part of our immigration policy is based on religious sects sponsoring immigrants to pad their membership (I have an unbelievable story to show this) and we all know about the Mormons including dead and/or non-Mormons into their church.