This happens because, in my opinion, they believe that every gamble will result in a profit, so even if they have lost, as you said, once they have enough money, they will most likely return to gambling and bet their money again. The bad thing is that they may obtain that money from illicit sources.
This really comes down to self-control. If someone has good self-control, whether they are wealthy or not, they are unlikely to withdraw the profits they have already earned. The opposite is also possible.
I felt sorry to watch them lose their salary because their family would be left without money. As if people were in a fog of illusions and did not realize what was happening. How did they survive with children? That is a big question. Perhaps they borrowed money from friends and colleagues at work to somehow hold out until the next salary. How long could this go on? After all, I witnessed all of this for several years.
You can't always help someone by giving them money, it has to end after a while and this has to happen very soon, the help you can give to these people can only be therapeutic and there is no other way than trying to grit your teeth and understand that you can't live on gambling alone, in fact you have to make them understand that it is absolutely important to manage your money