Don't gamble if you don't know anything about how it works or what could happens. In the end house always wins, otherwise there wouldn't be casinos.
These people never learn a lesson until something happened like this because they think that they can make easy money from these gambling sites. We should remember one thing that gambling sites are not doing charity work instead they are here to make profits for them. One should gamble only with the money which they are ready to lose. Otherwise, people may end up in this situation.
The main issue with these gamblers is that they want easy money, so they choose to gamble than any other hard way of working. Once they fail to earn free money then start crying like this. This is a hard way of learning a lesson after losing lot of money. As you mention we should always gamble with a small amount every time to avoid this kind of significant losses.