Reserving prison for the worst offenders has hefty benefits. First, it saves money. In America, for example, incarcerating a federal convict costs eight times as much as putting the same convict on probation. Second, it avoids mixing minor offenders with more hardened criminals, who will teach them bad habits.
…Rehabilitation programmes that focus on factors other than crime, such as creative abilities, physical conditioning and self-esteem do not reduce criminal behaviour, argues Edward Latessa of the University of Cincinnati. Boot camps are especially ineffective: they foster aggression and bond criminals together.