I agree with you that gambling addiction is indeed different from drug addiction. and the process for rehabilitating both is certainly different. but the negative impacts of gambling and drug addicts I think are equally frightening.
I would say the impact of gambling addiction is often greater than drug addiction, and I say this because when a person gets addicted to drugs, they usually ruin themselves only. Still, when someone gets addicted to gambling, they tend to destroy the whole direct family or people associated with them. Imagine a family man, having a wife and children and a good job, getting addicted to gambling, and very soon, everything is gone and they are left with nothing.
The aftereffects of gambling addiction are extremely frightening, less for the addicted person and more for the people getting affected because of it. The person who gets addicted will barely realize anything until it's all gone, but when it's gone and they see there is nothing left in front of them, I don't know what a person would feel in that situation.