Gambling ....

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gambling and earning are two entirely separate things; earning is generally risk free, while gambling is a simple game of chance. i dont know why people tend to think of gambling as some sort of source for income, but unless you are a professional poker player, gambling is not earning by any means.
I was actually going to bring up the poker analogy. There is some grey area between games that are purely chance and those that are partially or majority skill. I would consider poker to be a game of skill no matter whether or not you are a professional. I eeked out 5-figure/year earnings from Full Tilt before Black Friday in 2011 for a couple years and I wouldn't have considered myself a "pro."
I agree, it is mostly about skill, but luck plays a factor in what cards you're dealt. however, it ultimately comes down to the players ability to make the right plays, bluff, etc. most of the people here think martingale is earning for some crazy reason, when a game against the house is a game designed to make you lose.