With gambling at the beginning everyone decides of placing small amount, but if winning take place then automatically mind becomes greedy and makes the gambler to go for big amount. This at times described as sickness as well addiction when the person doesn't have a mind to concentrate upon other activities similar to a day job.
Everyone start gambling with small amount only, but once they began to win their bet yes automatically they will increase their betting amount. Yes in that time everyone will become greedy, so in that time nothing will stop them, for this kind of people gambling is considered as sickness.