A friend of mine also made this same vow but the only different is that he don't gamble everyday like your friend rather he only gamble during weekends and he have been doing this for a very long time now yet I don't see him gambling irresponsibly or even becoming addicted to it, even his lover ones knows about his gambling habit but they didn't say anything about it because he knows when he's supposed to gamble and when he's not supposed to gamble,so I think your friend case is quite different from this guy so i think he needs help.
This is how it should be, perhaps the term "gambling for entertainment" truly applies to your friend. He's not seeking a lot of money from gambling, and that's exactly what he should do. When someone learns to control their gambling, they won't chase their losses every day. Those who chase losses should learn from your friends, and must be accept if gambling doesn't have to be done daily, but can be done once a week with a small deposit that doesn't burden their finances.