If you're a gambler, then control and manage how you're gambling before it get worse to the extreme stage, also, if you're privileged to see someone gambling in the wrong direction, take it a responsibility to call them into order, some things were better done or dealt with in the early stage before they got worsened, having desires for gambling is not getting yourself harmed by gambling because if ignorance or lack of self control while gambling, the gambling platforms will not control you, it's your own responsibility to do so for yourself.
It is very rare that people listen to others when it comes to this as they will feel judged, and they will think that you are overstepping their boundaries by doing something like this, so even if you were correct on your observations about their gambling habits, you can bet they will continue to gamble as usual, and even if at some point they realize they had a problem you can be sure they will not remember that you tried to help them before things got out of control.
What you just explained is the power of addiction, the addicts never listen until it either ruins them or they just get delivered one way or another. Gambling is a very easy to infest activity, which calls for our careful engagement, and doing it sensibly and with a reasonable amount of money that we can afford to lose will go a long way in keeping us in check. You can imagine people who people started gambling with the mentality that they make huge money pretty fast from it especially when they read similar stories online even if it is fake. That mindset often keeps them in a bad psychology towards it and they might be forced to ruin money into it or get addicted thinking they can still get rich in it and also when they are persistent with it.
But some people would want to get back their lost money even if it is becoming unfeasible to be rich in it, but instead they will get to lose more. You see, gambling addicts come through different reasons and the reason matters to how the infestation level would be on individual gamblers. If the reason is so deeply rooted in it, there might be no willpower for the addict to say no anymore, neither would it work if you advise such a person unless they find external help from professionals or just got lucky enough to secure a better job that pays them well and/or take their time and attention away from gambling.