Always making sure this is brief as possible.
From my observation on addiction, i get to see how addiction is like a chain. Individuals moving from one addiction to another and how several addictions or one addiction can give birth/rise to the gambling addiction. We can all agree as an individual there are several things in life we can be addicted to aside gambling.
Substances like like alcohol or stimulants addiction (drinking), Nicotine dopamine and weed addiction (smoking), to mention a few others can influence a responsible gambler into becoming addicted. There are people in the society who gamble to humanize, smoke or drink, or go out on expensive rides and stuffs.
When it becomes difficult for someone is addicted to gambling to quit. I think its not just about quitting gambling he has to do, if he as any other thing he is addicted to he should first quit on those ones because quitting those ones might make him lose interest automatically in gambling.
You mention all the "bad" addictions but any addiction at all, like football card collecting, could give an indication that someone has those tendencies. Maybe those people with less bad hobbies are filling that need to collect or getting thrills in a different way (like opening a pack of football stickers and finding a rare one). I'd say things like smoking/drugs/alcohol are less about the addiction element and more about the stimulant side. There's a reason that casinos in places like Vegas are/were keen to give away free alcohol to customers, because it reduces their inhibition and makes them more likely to spend a lot more money on gambling for a relatively small cost. Getting buzzed off illicit substances can make it harder to correctly judge odds.