Are you a Christian? A muslim? If not, I don't think it is a sinful thing. Or is gambling in your country? If still no, why are you sinful? It is real life.
I think these religions consider gambling as a sin because of the reason of addiction, people often become addict to gambling and they do not care about their wealth and their future and continue to gamble with them. So I think in those games where we do not become addicted and play there only for getting some entertainment it will be fair.
Addiction is one reason, the most important reason is
greedy/love of money. In the Holy Bible, in 1 Timothy 6:10:
For the love of money is a root of all evils, because of which some, aspiring after money, have been led away from the faith and pierced themselves through with many pains.
That's why gambling is the sin in Christian life. But if gambling for fun or for charity, this is not a sin. Like in Nordic countries, gambling is for charity, casino earnings in Finland contribute 100% to the National welfare system, which is beneficial to the poor/unemployed/refugees.