~I think it's important to mention that sometimes people win when doing exactly what you described, and namely because of that this problem exists. If people were always losing, gambling wouldn't be around by now. But people should know that there are things you don't gamble with, and an amount of money that is significant for you is one of those things. So, even if you started from a small balance and then won big, stop and think whether you should continue, because maybe now it's an amount that you need for something other than gambling.
It is not like that a gambler will lose each one of his bet but most of the times, the outcomes will be against him. In the beginning, he might win more but eventually, his defeats are going to overcome his victories.
Because the house lures customers when they first start. Once they become a regular guy, house shifts it focus towards getting money from him. Hitting big jackpots must be the sign to go home.
The times when the things you described were happening are gone long ago. Of course there are still attempts of creating such sites by various scammers, and by "sites" I mean land based gambling facilities too, but only ignorant people play there. What you described is called rigging, and it's absolutely forbidden by law.
But I agree with you regarding going home after hitting jackpot.I heard stories about people coming home empty handed even after winning big earlier exactly because they didn't go home right away after a big win.