One big factor is, in a word, sexism. The traditional head of almost every church on the planet is a man. Mohammed is male, Jesus is male, hell even Buddha was, wait for it--a guy. Living religious leaders, from the Dalai Lama to the Pope - all playing for the blue team. What is wrong with this picture? Sex abuse, celibacy, no abortions, and every other way of keeping women "in their place." Women in the 21st century who go to church and run up against this boy's club...it's a turn off. I go to a Unitarian Church, one of the most liberal on the planet. But it has a long tradition of being run by men. It's annoying. I keep going because I meet people, men and women, who I like. But underneath the liberalism is a strong tide of traditionalism.