I agree with you if you are just an ordinary gambler and you are just going to play with your excess money and you are just going to treat it for fun. Then you are not going to earn with it. But if you have ample capital as you play gambling for sure even you are going to lose you are able to manage to get back your loses as you have a lot of capital. And most of the people that has a lot of capital with gambling they are the ones who are earning easily with gambling.
I don't really think they can earn an easy money over gambling cause their is no such thing as easy earning over gambling even if they have a large amount of capital it is surely not infinite to not decrease a certain amount of numbers right cause nothing would last that long in these world even a big company get bankrupt too, maybe the method in playing gambling are easy to understand but the randomness in winning over it would not required a knowledge cause it is just a mere coincidence.
That's right no easy money over gambling and the feeling we got to bet on something it's just a coincidence at the time of winning the bet and that too make us go to inside a trap of addicted.