It also happens with board games like billard, card, dice etc. In fact all sports. It is a general phenomenon that if you don't secure your early lead/winning by either walking away, you might end up losing all and your capital. That is gambling for you.
Most times playing poker with friends implies that those with more bankroll won't quit, and have to play until all they've got is exhausted. Basically, the last gambler would take the whole money, it could be similar to what happened with Op, and it's a rule that can't be boycotted, in as much as the person is also enjoying the game, because they've won with some couple hands.