I suppose in some cases it might help the rich to get richer, but in a lot of cases, perhaps most, people just don't know when to stop. For starters they're excited to be on the show and the further they go the more sure they are that they're headed for the big money. They're on a high and they just get carried away. They're gamblers. It would be all the same if they were playing the pokies and on a winning streak. Instead of quitting while ahead, they keep going and invariably lose the lot.
(I was like that myself once. In London in the 60s, a friend took me to a club and introduced me to roulette. I kept winning, so I kept playing. I walked away with nothing - lost a whole week's hard-earned wages. But I learnt my lesson - never again!)