This should be no surprise to any one who has known people with both problems.

Substance addicts are actually reliably happy for a while when they get their drug: but fairly fast, gambling addicts don't feel anything positive unless they score a significant win, which is always going to be a minority of the time.

My mathematics degree has done a great deal for me in the last 40 years, and one of those things is to give me absolutely no attraction whatsoever toward gambling. But that doesn't mean I don't feel a great deal of sympathy for those poor bastards that are addicted to it.