Listen, even that few percent you are talking about is just a mirage because there is absolutely no person that gambles comfortably with all assuraty of winning and making it a means of living. I believe gambler that do this are already develop in their real life career and are already making millions of dollars just like the way drake the musician and other celebrity gambler are going with their gambling hobby.
People don't gamble with the assuraty of winning because gambling itself is a game of probabilities so you don't expect a game of probability to come with any sureity it's only you taking chances and hoping to be a lucky by every trial but then let's not forget that skills and luck gives you a better chance at gambling than making just random picks.
This skill and luck is what some other gamblers depend on and continues gambling regardless of how much they loose to the casino gamblers who gamble with some level of surety are not only the wealthy ones who have got another source of income and do not depend on the proceed from gambling to make ends meet but also experienced gamblers aswell also at some point gamble with every form of surety because they are very sure with their experience they have a very good chance of winning, another persons who do such are those who have almost nothing to lose probably they just gave gambling a trial to have fun regardless of how wealthy or poor they are.