The only thing which comes to my mind is that gamblers in general are greedy. That's the only reason they always lose the profit which they gain from winning.
It's part of gamblers' thinking. We all want to earn and win that's why it's your responsibility to control yourself. If you lose control, you actually lose the money you're gambling.
If gamblers overcome the habit of greediness, they can earn good amount of money from gambling.
And also can lessen losing.