> making a parent a stay at home parent is simply economic reality for many

The topic was couples/cohabitation/marriage, not child rearing. The concerns you raise would be equally applicable where the parents have decided they want absolutely nothing to do with each other. There is truth in what you are saying, but it is an entirely different topic. How to deal with the child is a negotiation that takes place around the child, not around a romantic relationship (or lack thereof).

In the romantic relationship, there is no realistic situation where one party ends up with all the money unless the other one willingly hands theirs over. But any of us can do that. I can willing give you all my money now just the same and there would be no good legal recourse if I decide it was a bad idea later. The only reason we have these ideas in the world of romance is due to the historical idea that women aren't capable of thinking for themselves.