Addiction will not make them stop, because there are many reasons to keep playing. The more often they lose, the more addicted they become to winning.
Young people usually find it difficult to find their fun, therefore they decide to gamble because it is relatively fun.
Maybe they use their pocket money for deposits, because we know that there are gambling sites that have small minimum bets. So they can opt for that.
Changing games won't change anything, after all, they will only choose games that they think are easy to play.
You have a point, overtime the dopamine effects gambling has on the Brain can make people addicted to it, even if they lose they still find themselves engaging in this disastrous habit. When it gets to this point they don't care about winning or losing anymore, they are just after satisfying the urge to gamble more. Another reason why people get addicted to Gambling especially casino games is from the lucky tries that they have had, a friend of mine made a thousand dollars on crash games and lost over two thousand dollars, he became addicted because he saw how easy it was to make money and fell into the trap.
Yes, that is the worst addiction situation where a gambler no longer cares about winning or losing, all they want is to keep gambling as you said because they feel comfortable with the increase in dopamine that occurs in the brain due to the sensation of the game they are playing and want the game to continue while the risk continues to lurk so of course it is very possible for them to lose a significant amount.
On the other hand, as you said, now your friend has become a victim of addiction after successfully getting a fairly large win but unknowingly he has lost an amount of money that is much greater than the win he ever got, that's where the casino is smart, they first brainwash the gamblers with something very tempting at the beginning which makes the gamblers have high hopes of getting back such a win.
Therefore, the point is to be wise in responding to everything, use your rational mindset, because that way I am sure that you will not be tempted by anything that seems too easy to get.