Why would you even trust gambling where you cannot control anything on it just the amount of bets that you would take? I believe this boils down to what you can do and the self discipline that one should have when gambling.
You don't need to totally trust anything that you don't have a total control over because the outcome may or may not favor you. It's not restricted to gambling alone, but since the focus is on gambling I'd say that you should concentrate on the one area that you have a total control over. A gambler needs to understand bankroll management and how to apply it when gambling because you don't know whether you'd win or not. I wouldn't advice anybody to trust gambling as a source of income because it is not a job, use the amount that you can afford to loose.
As much as possible, no one should make this activitiy as a source of their income especially if they are into classic games. I can understand if they are professional poker players or a long time sportsbettor because this kind of gambler can indeed make a living out of their respective gambling activities. But if you are into luck-based games, you will likely lose your bankroll and you need a serious bankroll management in order for you not to lose it all.
It seems to me that you overlook that many gamblers play for dopamine and adrenaline, which are produced in our body not only during winning, but also during the waiting for the win and during a strong stressful situation when the gambler significantly exceeds the risks. Gambling addiction is just provoked by the fact that the gambler wants to get these feelings again. Most gamblers are well aware that in the long term casino/bookmaker has an advantage, but still continue to gamble. This happens precisely because of the desire to get dopamine and adrenaline.