More than 50% of the world population gamble in one sport or the other and some are making good money while some are still hoping and praying for their luck to shine.
Isn't it obvious that you can't make a "regular" income thru gambling? Because for me that is the definition of source of income. That you have a regular job that you got paid bi-weekly and monthly. And with gambling, it's very hard to do that or it's impossible. Sure you might win one time, but it's hard to do that again and again and duplicate it. So there is no doubt that gambling can't be a source of income.
Unless you are a gambling operator, casino itself, or running a illegal den in your country wherein it can rake a lot of money. Or one time, you really hit big by winning the lottery and it did chance your life for the better.