Who said gambling will always be loss in future? There are both way returns like profit/loss and you need to be sensible gambler to balance your situation well and that's it.If you are not professional then you can enjoy with your small bets only.
You just don't go beyond your limits and keep up your budget if you don't want to end up in worse situation and play in well manner.
Are there really a lot of gamblers that end up in profit ? I doubt that as in the end, the house always wins. I know there will be some good days where you have a lot of luck but most of the times, if you keep playing, you will end up with a loss.
Technically speaking you could be able to finish with some profit, in the end we are talking about something that would be quite profitable for everyone and it is going to be "leave when you are ahead".
Not many people do it but the reality is that if you could do it then it would be quite profitable and you could leave like that. Obviously, most people profit and then keep on gambling and lose a lot of money, I knew a ton of people who have done it that way and lost a lot of money. But, I have a friend who wagered on sports and he once earned so much money from one parlay he had that he quit cold turkey because it was a good amount and he didn't want to lose it back.