Stories like that are very common and I agree with the OP on their theory, if a person only lost money when they gambled then it would be very difficult to get addicted to an activity that was always punishing them in such a relentless manner, however if you happen to win then you will begin to chase those profits and that feeling, and while there is nothing wrong to do this with moderation, this could eventually lead a person to develop a gambling addiction if they cannot control themselves.
People tend to be moderate with their gambling activities initially after they get some wins in their very first gambling session, but they start losing control as they start going deeper into the well of gambling addiction. If they go gambling for the second time after winning in the first session and then they lose some money, they might not be that much interested in gambling, but if they manage to win more in the second session, that makes it more difficult for them to stay away.
So, the first few gambling sessions are basically the deciders of what a person would become in the gambling industry, whether they will stop gambling, will become a gambling addict, or will become a responsible gambler and only use a limited amount of time and money on their gambling activities.
Something very similar happens with trading as well, in which if a person invest in shitcoins and they happen to earn money then they think that trading and investing is nowhere near as hard as they were told and they are incredible at it, then they keep investing pursuing those easy profits until they begin to lose, then they refuse to accept that they were lucky at the beginning of their journey and they spend the rest of their lives trying to recreate that early success they got.