If you ask a therapist who specializes in addiction, they will likely say that gambling addictions are the hardest to treat. The reasoning is that when one gambles, one actually wins sometimes, even after many years of gambling. It’s that occasional reward that makes it difficult to treat.
Drug and alcohol addiction, after years of abuse, do not result in “wins” of any kind (NB I did not say in the beginning of the addiction… but years later)