No matter how reasonable an advice is from someone that's not addicted to gambling, it's futile because there's no way that gambling addicts are ever going to hear it or follow that because reasoning with them doesn't work, self realization is the only thing that's needed before they can start hearing out some advice, as the saying goes, you can't really help people that don't ask for help, it's not really your duty to save them anyway, give out the advice and let them know that you did your part but never put too much effort into it because they'll end up hating you for it.
I think that if we know the gamblers personally, of course it is not wrong to just try to remind them, but after one or two times our advice but they do not listen, of course it is better for us to no longer interfere with their lives, because as friends at least we has tried to change them but it is they who do not want to change, it must be admitted that gambling addicts are usually trapped in a mindset that makes them reject advice and logic, Not because they do not know the truth in the advice, but rather because they have not reached the point where they are ready to accept it, so it is better for them to find their own way after we try to warn them.