There are reasons, but probably not the ones we think. Their parents' hearts are broken. Aliens from God, outcasts from society, these poor souls are without hope for this life or for the life to come. He looks upon them with pity. The problems that conservatively reared young people have with drugs and other druglike compulsions do not develop in a vacuum.
Circumstances play a part.
Our children's negative behavior is as much about our homes and churches as it is about them. We adults assume that the self-destructive behavior of our young people is attributable to lack of conversion, parental neglect, institutional failure, or the church's inconsistency. The development of such tumors into full-blown, overt addiction may require years. Throughout that time, the pathology may go virtually unnoticed. It may even take more than one generation to manifest itself, appearing subtly at first, not revealing itself in its most malignant form until the third or fourth generation.