Some people raised some interesting questions and points to consider that merit some further exploration. The first is that in all denominations, the faith of the parents is the most likely factor to contribute to a young adult choosing not to return. This specifically refers to the willingness of the parents, especially the father, to be transparent about what lived and articulated faith is about. A nominal faith that is very private is typically not passed on to others.
Another factor is the consistency of faith. Too many times children and youth pick up the hypocrisy of their parents as they live out different values depending on the company they keep. I remember in my first "secular" job working in an office of a manufacturing facility, I was really surprised at the values expressed by many of my co-workers who would have presented a different face as they went to church on Sunday morning. This stuff matters and our children and youth are the first to see right through us.
There has been a popular notion for the last 40 years or so that resists inculcating faith in our children. The idea simply is that parents should not be coercive, but let children find their own way. It is true that there should be space for questions and exposure to other points of view. But this attitude toward child-rearing has been the predominant model in mainline Protestant churches for years and has had devastating results. It sounds wonderful and tolerant but in the end it simply ensures the demise of a lived and passed on faith. We should be advocates for the realities of God's presence in our lives and in the lives of our children, youth, and young adults.
Parental efforts do become counterproductive with their pushiness if hypocrisy is a factor. And we do see too many young adults carrying wounds from childhood experiences from churches and families that are just going through the motions or possibly even abusive.
No matter what your background, as adults we will need to own our responses to what God does in our lives. Living a certain way is not a guarantee that our children will choose faith. And many, many people throughout history have moved beyond the difficulties of their childhood and chose a better path for their lives.