Frankly speaking, gambling is not easy and we ought to know what we are doing to make money from betting.
Few people have ever managed to stop gambling and look back and say they made a profit. Most people make losses and honestly people should not think that they can pay the bills by being a gambler. They need a job or a business in the real world. That is why it is recommended that one looks at gambling as just fun.
Of course, gambling is for fun and not a means of living because the consequences of using gambling as a job is bigger than what you think it is. Gambling will only bring losses to you than profit, and that's why you should only gamble with little amount of money that you can let go to avoid emotional trauma. Take your job seriously and only gamble for fun.
Yes that's right and maybe I will complete your idea that one of the reasons why gambling is really prohibited to be used as a place to earn is because there is no way that can guarantee victory and also there is absolutely no consistency in achieving results, the only problem is how can you make a place that depends on probability and luck as a place to earn income? and that is the reason why the opposite happens, as you said that making gambling a place to earn will actually make you lose money instead of earning and that has been proven, in the end as you said that this is the reason why we are always advised to only make gambling a place of entertainment and not more than that.