I am very confuse about what they call the gambling a game >.< its about spending money on nothing then why is it called a game? why don't call it money investment? kindly explain please? Thank you 
Games are fun and they want you to have fun. Casinos want you to feel gambling is fun and games. So that you "play" more but really just fuel their profits. So they make it feel as much of a game as they can.
I hardly think that 10% of real gamblers would gamble for fun, I mean what is the fun in loosing your money ? I am not quite sure.
Yes though gambling was made for entertainment but since the involvement of money everyone has started to just starve for profits and hardly anyone plays on casino's for fun anymore.