I'm muslim. For me it's sin absolutely. Because Kuran doesn't let it. Undoubtedly, for my religion gambling is devil's trick. By gamble devil make breaks between people, and keeps away people from worship and their religion. But I think on other religions playing on casino sites is not sin. In general, no benefit from gambling.
Your religion is trying to protect you from gambling problems. If you are taught for your own benefit then you may or may not follow some belief. But if it is being taught in the name of God then definitely you will obey to that. Gambling is a thing, every human must avoid, when it is categorized as sin then we should not touch for any reasons.
While most people can gamble and suffer no ill consequences of doing so, there is a small minority that will suffer the consequences and that is why religious authorities try to protect them with rules like that but unfortunately for those that cannot control themselves most of the time the rules are not followed.
Religion shouldn't be a general reason i guess ,
Take it personally and we might good to go to discuss about this ,
When you have a strict environtment around you about gambling then just obey it ,
Gambling is a sin or not are your own responsibility , just don't harm people .
If you are religious, or if you feel you have a religion, then you have to do everything and treat everything based on religion. Because if you ignore the rules of religion it is the same as you do not believe in your religion. If you want to gamble, then you should know the gambling law on your religion. Once you know it, then it's up to you, just make sure you continue it or not.