Easy maybe for those who are doing it just pure for fun and killing some time, but difficult/tough for those who already engage and believing that they can change a lifestyle if luck will back them up and win decently.
For those doing it for fun or entertainment they mightn't find it easy to quit as well because when they get addicted they will have similar behavior like those playing for money. They won't want to quit even when they're not making profits. Addiction is very hard behavior to quit.
The only time a gambler can quit gambling is when he isn't addicted, it doesn't matter if he's playing for the money or for entertainment, provided he isn't addicted, he can stop gambling at anytime. There are some things anybody wanting to quit gambling needs to know.
Whether it is for fun or to make money, someone who gambles regularly has the potential to become addicted. But those who think of gambling as fun have little interest in money or no adverse reaction to losing money. I agree with you that if someone is addicted to gambling at any stage then it is not easy to give up gambling. A gambler is not an addicted gambler if he gambles and is able to take a break from gambling at any time. I also think it is a very effective method to pick out an addicted gambler.