Gambling is both a business and an entertainment because that depends on the players that play the games that would involve gambling. Some people say Gambling is just Mathematics and some players really got the skills to play so they are treating it as a business in which its a source of their income. Other people only gambles when they got money to burn and that is why for them its entertainment.
No matter what the person thinks or believes that doesn't change the fact that gambling for the gambler can not be a business unless they are using some kind of a trick or found some kind of a bug in the system and that way they can control the outcome of the games to a degree that can give them an almost stable source of income, in any other cases which is like 99% of them it is just gambling and you should treat it as entertainment, only the ones that are owning the casino are running a business and can count on it to give them return.