Some religion doesn't allow gambling, bacuase its related with greedness.
There are many people in the world who think it is sin to gamble. Although I believe that it is no sin to gamble, but it is not the same with my parents. They think gambling is a very bad habit and destroys a person. I believe that if we do controlled gambling then there would not be a problem for us, but if gambling turns to greed instead of fun, it destroys many lives.