Through much of the 20th Century, reformers were trying to turn the 'juvenile justice' system into one based on rehabilitation. A private, for-profit prison industry has no incentive to rehabilitate anyone, especially kids. Turning the juvenile system into a feeder system for the adult prison industry just guarantees continued profits.
Sometimes I wish I believed in Hell! People who destroy the lives of young people for profit deserve to burn in one Hell's hotter circles!