Our relationship with money directly impacts our relationships with people. If we make poor and emotion-based financial decisions it negatively impacts the people we have in our lives. I guess when couples make decisions, they should try as much as possible to take emotion and other forms of bias out of the equation. And the thing is that bad decisions made by couples even go as far as affecting their unborn children.
At the extremes, we can look at the impact of gambling addiction on how bad it can become, but also all the little impacts along the way.
I think this is why a lot of people aren't having children now. Not just because of the cost of having them, but the cost to their own spending on the things that they want - most want to keep making bad decisions.