take a closer look, the quest sdo not once tell you they are addicted, the situation is explained as they are starving - they now can only ingest arcwine - the quests tell you why that is the case. The city ran out of food, they came up with a way to convert the nightwell's energy/substance into an ingestible form, they called that arcwine.
unknown to them, the corruption in the nightwell over time has led to their bodies rejecting any other form of sustenance. This is not an addiction any more than you would call needing food an addiction. If they don't have arcwine, they wither and die, their bodies becoming corrupt, essentially starving.
Not once are you told they are addicted, players jsut jump to that conclusion, because the withered crave mana like the Wretched do, and don't pay attention tot he story - watching too many streams from beta testers who care more about the cool loots and moves than what's actually really going on.
The nightborne will become corrupt if they don't take arcwine, if they don't have their own food. the blood elves become wretched if they over-indulge and give in to their addictions, it's the opposite of what the blood elves have.