Why do they leave when they graduate?

I am thankful to hear that there is a stirring in some of the leaders within the churches of the Jefferson Baptist Association (Jefferson County, Missouri). Recently the question has been asked, "why are teenagers leaving the church when the graduate and what can be done to keep them." Well, I would love to have a little conversation about this for those who would like to chime in. The reason why I am excited to hear that there is a stirring is because I think that people are waking up to realize that many, if not most, of the people in our "youth ministries" today are unregenerate and have never experienced the "new birth" that is in Jesus Christ. Second, there is a different phenomenon going on...that is that we are seeing people that are "graduating" from youth ministries and they are not entering in what should be "mature Christian adulthood" within the congregation. They are half-hearted about participating within the body of believers, they don't really know what it means to be accountable, etc.

There is a book that I am reading through regarding some of these issues. Now, as I would not agree with everything in this book, it has been useful on some points, and I would like for our Student Ministry Team at Rockport to discuss it's contents. The name of the book is "Family Driven Youth Ministry" by Mark DeVries. It has been sitting on my shelf now for quite some time and I am just now getting around to reading it. On page 26, I would like to quote the following statement.

The crisis in youth ministry is, simply put, that the ways we have been doing youth ministry have not been effective in leading our young people to mature Christian adulthood. Even with the massive increase in funding and training for youth ministry, even with the exponential increase in the number of resources available to those of us doing youth ministry, we are seeing no appreciable increase in the percentage of adults in our culture who are living out their faith for themselves.

Now, obviously there are some flaws with the above statement, however I would like to look at the intent of the quote that we have failed to present people as "mature Christian adults." I can't agree more. Perhaps the reason is because many, if not most, have failed to actually preach the gospel in their youth ministries (like me), thereby most of their teenagers have never heard their need to repent of their sins and to trust in Christ. Or perhaps even those with a great teaching and preaching of the gospel, fail to realize that having young people together just for the sake of "having young people together" makes no good sense at all.

Well, I have already commented more than I wanted to for this first post, because I am curious what others would say to this.