"Azkaban was not meant to permit anyone to recover, no. It was made as a sadist's trap, both to keep people in and keep the Dementors away from everyone else."

Long ago, when the prison was first conceived, wizards had not the means or spines to eradicate Dementors from their world - or perhaps some of them were fascinated, and wanted to keep a piece of that darkness around. What better way than to feed and isolate them? And so, this habit began, instead of the kindness of execution.

"The theory is that if you shove the same things that deter a Dementor into a person, it'll rebuild the decay."

That sounds kind of unpleasant, Professor.