Inspired by this thread: The religion you believe in - Why did you choose to believe that religion?
I'm not talking about religions where a passing familiarity was enough for you decide they weren't for you. I'm talking about religions that you were once immersed in: the ones you seriously considered a participated in, or where you were a full member.
If you are no longer a part of a religion you were once in - or were at least on a path toward - why did you reject the religion?
I rejected Evangelical Christianity, in brief, because it's intellectually shallow and ahistorical. I rejected Catholicism because I eventually found that the whole Christian house of cards came tumbling down when I began learning more about the very human origins and contents of the Bible and realized the Church had poor rationale for a number of its teachings.