Not all gamblers that plays with a small amount of money in order to win big amount do so out of greed it could be that the small money of $10 was the amount they had with them at the time of making the bet, some however, do use small amounts as a means to be able to have many chances of playing to try their luck instead of using all of the money at ones. While some are just mere greed, they want to win even more than a $100 with just $5, even if it's possible with luck setting in but it's rare to happen and before it does you could have lost many times more than whatever amount you will be winning.
Yes, that's true because each gambler has a different fund allocation so they will gamble based on their fund allocation. But most gamblers who use small bets and can win large amounts of money will try to gamble again to win even more. Even though it is not recommended, that is what happens to many gamblers so it only increases the number of losses later. We cannot hope that luck will remain with us in the next round so that the final result will remain uncertain whether we win or lose. They may only be able to continue gambling but have to accept the risk if they lose because they desire to continue gambling.