That's the situation if the gamble did not try anything new or trying to develop his own skill for better gambling. If people only depend on their luck to make profits in gambling then they must loose in short term as well as long term. Long term will give you time to rectify your mistakes.
That is the wrong way of think for most gamblers, they are think they could profit for a long run with it, you will lose it all in a long run because of house edge, gambling company and sites has an house edge to prevent them from bankruptcy. that is why you can't make a profit out of gambling.