I wish we could survey folks as to why the leave. I reponded “Mainline Protestant” in the survey since I think people go to a more liberal church for their prochoice views, same sex marriage etc. The ultra liberal Unitarian Universalist Church grabs many since it openly welcomes gay, lesbian, bi-sexual and transgender individuals, deists, theists, atheists, agnostics, wiccans and pagans.
Others leave life totally, as in they just dont go to church, or they simply worship at the mirror, so to speak, as many have said in this thread. Material goods become their god in the “church of me.” Possibly the philsophy of secular humanism grabs them because of the permissiveness.