> Potato potato, that person would not have been in prison had they paid off the debt.
No. The meaning of words matters. Words, used precisely, are how people with different values and beliefs can communicate and reach agreements in a functioning society. When journalists, who are supposed to inform and educate the public, twist the meaning of words in order to make a point, that’s wrong.
> Where the debt comes from matters why exactly?
Because a debt arising from a criminal conviction requires the convicted person to have engaged in a wrongful act in the first place. Mere failure to pay a civil debt does not.
> The prison should be for one purpose only: to make society safer
Views about the proper role of prisons vary widely. Most people believe that prisons are for punishing people for doing bad things. Note that by your reasoning, many people who do very bad things should not be imprisoned because there is no risk of recidivism. Women who murder their abusive husbands, for example, are almost never going to go and murder someone else. By your reasoning, they shouldn’t go to prison to punish them for their murder.