Most of the people behind bars are not there for reasons of 'organised' crime: They have not sat down and done a rational cost-benefit analysis of their crime and sentence before going out and doing the deed. 
Most people are there because of a failure to manage their emotions at a crucial time. Often - not always - drugs and alcohol play a part in that.
Exercise and physical activity give people a chance to practice the skills of managing their mood and to experience agency over their thoughts-behaviour often for the first time. It is the reason why Andy does what he does in the way he does it, and here he explains it a little bit more. 

These podcasts don't get made unless Tom Haigh of Sound Post Production www.tomhaigh.com and interviewer Tony Maguire www.boxkik.com decide to roll out of bed. Fortunately for me I still seem to be giving them reason to do so. Chapeau, gentlemen.