Of course, there are people who earn their living professionally from gambling. They know math, game theory, probability laws and other sciences well. This kind of income is not available to everyone and he who earns money in this way does not share his secrets with other people.
That will be only a few people who can earn money from gambling, and as you say, they know the most things of gambling so they can win every round in the gambling games.
If other gamblers follow their way to make gambling as a way to make money, they will difficult because they don't have more knowledge as that person.
Gambling can be a profession, but it is not for all of the gamblers.
It will need more than skills to be the pro gamblers, and the risk is too big to imagine because we can lose everything we have to be a pro gambler.
We never realize how hard to be a gambler, and we all want to get a win in the gambling.
But for me, I never think that gamblers as the way to make money, I don't think that gambler is a profession because we need money to make more money.
I don't think that is right to do because I am sure that in out there, we will have another profession that will have less risk than gambling.