One of the reasons is the issue of origins. Many young people view Christianity as anti-scientific. They are also turned off by the evolution vs. creation debate.
In a book written for high school students, Professor of Science & Religion Denis O. Lamoureux offers various ways to develop a positive and productive relationship between Christian faith and modern science. He also shares his story of losing his faith as a young person, and later returning to the Lord. His approach to origins is ideal for developing critical thinking skills and for honoring Jesus' command in Matthew 22:37: