In Singapore, local residents have to pay an expensive annual fee to the government in order to be allowed to gamble in casinos, while foreigners may do so for free.
The money collected from exclusion fees is quite large, 100s of millions in some cases in a year. The very fact that the collections are so big points to a possible fact that exclusion fees are not a deterrent or stop/reduce locals from gambling.
In Korea, by law you have to prove you're a foreigner. In the Bahamas it is legal for the locals to bet, but the casinos kick them out. They've had enough experiences of a guy coming in on payday, losing his money, then his wife coming in the next day with a baseball bat to destroy the machine that took the money. Don't want any more.