Another very early essay which needed updating: Why Do Teens Deal Drugs?
Admittedly it was not a rigorous analyses of all reasons but of just a few. On this most recent update a few more were added. As time permits it may undergo a major overhaul to find and categorize every reason.
But as usual the bottom line is that Prohibition was and remains the primary reason for increased teen use and involvement in the trade, primarily and explosion in the rate of involvement in the last stages of the Prohibition-created underground market.