I suspect the reason is that they do not have to be born-again, can live like the devil all week, confess to the priest, eat the little wafer, sup the juice, and live as if everything is ok because they have just enough religions to soothe their dead conscience.
I love westerns. In one book by Johnstone, the hero shot some crooks. One was nearly dead and asked for a priest. The priest arrived and the crook said something like, “Father, I have sinned.”. The priest said, “you sure have” and walked away