It is acceptable that most of us can't really do this but I take it into consideration that some can do it like they really are living to gamble, born as gamblers.
Some people can think they can live with gambling but later find out that they are wrong after significant losses. Anyone that is thinking that they can make a living with gambling is deceiving himself until he finally realizes that. No one should depend on gambling, it is a game of luck and the luck is more towards the gambling sites. Gamblers should not take their financial life a joke, they should not depend on gambling.
If we're going to analyze it deeper, on the other hand, gambling is a source of income for those that are working in the gambling business. But, since it wasn't the thing that OP is asking about and just plainly as a gambler, I agree that it's hard to make it as a source of income.
You are not right about this, how can gambling be a source of income when there are chances that you are more likely to lose while the gambling sites are more likely to win? Gambling should never be taken as a source of income. Because you make profit from gambling today should not be seen as a good reason to see gambling as a source of income, because it is not reliable.