It's hard to understand why they cant just stop. Could be due to mental health problem or lack of support. It takes a lot of courage, willingness, and determination to break free from addiction, so it's recommended for them to seek professional help to have successful recovery.
You're not in their shoes, it could be a lot more harder for them to understand why they have an excessive urge to gamble.
Yes, It could be mental health problem, but most addicted gamblers are not aware that they are really into a sh*t situation, not until they realize they've already lost everything.
Lack of support? Nah, If that person is not interested in cutting of gambling completely out of his daily routine, that support means really nothing. You can force him to go for a rehab, but most likely he's still gonna come back to gamble. Combating gambling addiction starts from ones self. Otherwise, It could be a very rough journey forcing someone to withdraw against gambling addiction. The same goes to people who are alcoholics and drug addicts. Even cigarette addiction is really hard to get rid off. Sometimes you'll get withdrawal sickness.
Addiction can be stopped, but hardly will an addict quit gambling. Addicts are informed to stop, not quit because it's impossible or not wrong to gamble. We only try to remind the addicts that they're going quite too fast into destroying their emotions. When we argue this with the addict, he develops a countervailing reaction. He could blankly stare at us for uttering such words. The addict is emotionally detached from whatever is happening around him. Hence, his attitude is centered on what he believes in gambling. Nothing else could get him out of such thoughts.
Gamblers who are into such problems, lose old friends and hardly will see a fresh one. If one is opportune to have help around him, sooner he'd be fine. And have a change of mind. Although we all need to be smart on this and act professionally. It's a mind game, and they must be a winner. Going to show the addict your plans towards him are a threat to him. He'll get prepared waiting for any moment you tend to reach out to them.
He'll also prepare his answers to whatever questions he presumes you'd ask him that day. The conversation can't end in peace. That wasn't a conversation, anyway. It's a mental tug-of-war. Relieving this stress helps reduce the problems of the addict. He needs to focus on whatever he's doing. We can only be of help when we claim to be or act like him. Picking up the best possible means of being of help to him, works faster. The relationship we build with the addict while on his side, makes him hear from us.
Isolation is bad emotionally for any human, addicted or not. Humans are meant to network and communicate with people around them. Naturally having conversations not relating to gambling with an addict, helps sharpen his thought for a minute or two. Continuously doing it can change his brain entirely to that perspective, which you seized the opportunity to embed in his thoughts. The goal isn't to make him quit but to stop him from compulsive gambling.