Addiction has no age. Wether you are an adult or not, everything which is too much should be stopped.
If it is on gambling, then it is clearly very bad to continue without realizing what the effect will be in the long term.
Privillege indeed has many sides; you can use it as an advantage in life or it may consume you as an individual to be too comfortable with life and with lacking responsibility of different things. In this case, parents themselves are guilty of what happened to their child but let's end it that way. As long as they are aware between right and wrong, behaviors can still be changed for a better. If rehabilitation would be needed then so be it, because if nothing will be done in order to stop a behavior expect the worst such as leaving them all with empty-handed or them being uncomfortable with life without this activity which hooked them up.
Demographics is probably the reason why a child is free to do anything beyond his parents' control when he is 18+. In my country gambling is still the reason why you are said to be a bad person to be guided, obviously this is the norm in society which may differ from country to country. But whatever it is, I don't think it's a big deal for the billionaires out there to be afraid of because they might really want to see their kids enjoy a life of luxury or whatever.