Gambling can never be a source of income. It is rather the worst source of earning and best source of losing money.
If a casino owner reads this, he will start laughing at what you are saying. You have to figure it out and categorized on who are going to make it as source of income. If a normal gambler does then it's hard for him to make it for a living. But if a real life investor and businessman will make it as a source of income, how can you say that it can never be a source of income?
Sure if we want make the gambling as our main source of income then we can make it but succeeding with this as our souce to live is hard.We have to keep other source as job and can allocate few mkney for gambling daily if someday we are lucky then we can make it to successful.