Well, I pretty much agree with the logic here, if the family isn't so well-to-do and doesn't have a lot of money, rejecting such an amount is sheer stupidity, because as you said, beliefs or culture or any other thing won't pay the bills and money is a basic requirement for today's world, you can't do anything at all without it, and if wealth is knocking on your door, you should welcome it with open hands.
The family head which is the fsther have messed up really badly and this shows to a great extent that the father doesn't have love for the son, fine if the boy has gone the extra mile to gamble which may be against most religious mindset but it it we have to understand the impact of this rejection on the physiological well being of the boy.
Now, instead of guiding the son on the way he will spend the money without becoming addicted to gambling and how to make a withdrawal mechanism and reinvest the profits, it will become hard for him to control the boy's actions if he rejects him outrightly.
Depends on a certain child or son because there are ones who are really get used to on what their fathers reactions or behavior on something that they had done specially if its against on his father principles but as a child then we cant really know whether those ones would be good or bad unless if he/she's fully aware of it then you would know that it isnt really that right on telling to him in the first place because you do know on what would be the reaction which it would really be that situational on this case. We cant really that tell on how a children that been rejected will really be making his next step
whether he would take it seriously and emotional and pschologically be affected or would really be just simply ignored.
If im on that situation then i would definitely be spending on things that i do like rather than on giving it back into the casino on where his Father suggested which is really that a dumb idea to be done.