Every marriage have this same problem with their partner. In fact most monogamous marriage have ended because their partner doesn't contribute to house chores.

However, I haven't heard of a poly marriage ending because their partners are not involved in house duties.

And if you read my title well, I said the main reason. Yes, your point is one of the reasons most poly (as well as nonpoly) marriages fall apart, but that isn't always the reason women regret opening their relationship.

If the house chores were the case in poly relationships, they would leave their partners rather than suggest closing it. From my chats with poly married women, jealousy is the main struggle they've had to deal with. But they try to keep their emotion under control because they enjoy the freedom of dating multiple peole.