Gambling only because a problem of addiction if one allows it to be. It's almost the same with how other forms of addiction work so that's why I agree that even constant winnings can contribute indirectly to the addiction. One mentality that fuels gambling a lot is the fact that in gambling, you can only lose 100% of your money but you can win as much as 1000x worth of profit.
If you do it long enough to convince your brain that it's a need must situation, then it becomes an addiction.
It is yourself that is your enemy here. Addiction comes from days and days of playing without thinking that one day, you will get addicted. If you are not checking your lifestyle every once in a while, the chance that you will head to addiction is high as you are not assessing where you are now at your supposedly side hustle.