[...]if that's the case who should quit for who.
Battle of the sexes? If you're going to ask this hypothetical question then at least provide more context like who is earning more and providing most for the family expenses. It's traditionally the Father's role but if this marriage is a 50-50 then both of them has to reconsider their gambling activities. I wouldn't say both should quit if they're able to manage it to a minimum.
The question really need elements like what you ask, it's the winning that determine who can drop for the next but they can still balance the situation without any quiting through rationalization of how they will play it even with children not been harm or lure into it all because I have see family who parents gambling, smoke but their children don't partake on such activitiesz be if the win from the couple are always 50-50 it's going to be a serious issue where one will drop completely though it's a matter of understanding. There are some family where responsibility are share stating that the woman news drop because of the man responsibility may not be right because in the family Carey out responsibility too.