The Catholic church is an ancient, dusty, mysterious institution rooted in the Middle Ages. Its wealth and history (of good works and horrific abuses) is legendary.
My grandmother was raised in a Catholic orphanage; she sent her children to Catholic schools until my aunt led a rebellion. Not one of them stayed in the Church. My mother wouldn't own a pair of black shoes because she had memories of looking down at nuns' feet while they lectured her. I was only baptized because of the hectoring of a potential godmother (so I wouldn't end up in Purgatory or worse), and have never attended--save for the occasional wedding or funeral.
I imagine several factors come into play for adherents: the community culture--some areas are more churchy than others, family tradition, affinity for the pomp and grandeur and history of the institution...I will say that I admire Catholic churches for establishing religious theater in a way other sects can only dream of.
I'd like to say here that I am grateful to the Catholic church of Spain for the Inquisition. It made things so hot (pun intended) for my SO's relatives that they fled to Mexico. Without their emigration, I likely never would have met him.
