I know that gambling is forbidden in Islam, I doubt that it's specifically written anywhere in the bible that christians should not gamble, although I've heard some overzealous preaches condemning gambling as a sin. I don't really know about the stance of other religions regarding gambling, so I think that it's mainly Islam that is very vocal about forbidden gambling.

I think that the way majority of people view gambling is based on their personal decisions, not religious believes, therefore it's their choices whether it's morally suitable for them or not. You will see people who don't belong to any religion condemn gambling, due to various reasons like gamblers are financially irresponsible, while others sees it as a normal game that people engage in, where you'll meet responsible and addicted gamblers. So gambling is more of a choice than believes.