Why do/have a lot of Catholics leave/left the Catholic church ...

On Yahoo Answers someone posts the question: why do so many Catholics leave the church. The winning answer is:

Most likely? They never truly learned what the Church taught and offers.
If they really understood what the Church is, and what she gives; they never would have left her.

One of the losing answers is a raving paragraph on the mysteries of quantum mechanics, teleporting and an infinite amount of universes. And of course, this person believes that religion is bunk, the universe is random, and there is no purpose to any of it. But most audaciously, they list Abarim Publications' celebrated introduction on quantum mechanics as a source of their lunacy. The only just element of this post is that it received a generous zero percent of the votes cast. Good.