I would add my comment that once they do and get into the Bible, they usually come back with a better understanding of what Catholicism is about...if the Church could just open the Bible to them in the first place I doubt they would ever leave. More about Jesus, less about the institution that exists to make Christ present.
From Homiletic and Pastoral Review
An Operative Theology of Exit: Why Catholics Leave
- Lack of active participation
- Lack of scriptural and theological sophistication
- Lack of appropriate and effective Catholic catechesis
- Anemic parishes and preaching