It wasn't just addiction. He had enough U-47700 for 30,000 trips (30 thousand). See https://news.ycombinator.com/item?id=44291172
Simply saying "you did a terrible thing, and that's irredeemable" isn't useful to society. What good are you doing if you've rehabilitated the criminal? You're just spending tax dollars on principle. It's cruel and unproductive.