From my part, I haven't seen a single person who has benefited from gambling (other than the owners of the gambling sites). Some people were lucky... earning quite a lot of quick profits in the beginning. But even they gambled away their initial profits and then slid deeper in to debt, when the addiction took hold.
I don't disagree that gambling can be addictive and destructive but so can alcohol and sugar but there are plenty of people who make a living from gambling or just enjoy it without any problems. It's about moderation and control but obviously some people don't have that and the fun quickly turns into habit and dependance.
Their "wins" are temporary. Gambling is highly addictive. One day, you will win $100. And addicted by this victory, the next day you will put in $1,000 and lose them all. I have seen many such cases myself.
Not always. I'm sure most people do lose more money than they win and the longer youu gamble the more likely you are to lose but you can be a winner overal if you pace yourself and stick to your budget.