Gambling is so addicting because of the money. Money is the root of all. You will do anything to seek money. Even it is bad or good. Wrong or right you needed money. So gambling are more addicting and enjoyable because of money.
not all gamblers would like to have the money, there is also the gamblers are just looking for the sheer pleasure in the game. they feel the happiness that they can not feel in any other game.
There are people that are just for pleasure but they are very few. Because even those rich people that are gambling, they are into profit and they are even making it as their main goal when they gamble, is to expand their money by gambling it along. I don't know if those people that are just for fun are aiming for entertainment 100%.