“She is making all the purchasing decisions”
This is the failure in your screed. Dave espouses that both the husband and wife are involved in ALL purchase decisions. In fact, the budget is an agreement between the two and is a monthly reminder to them that they need to be in agreement on their money plans and goals.
2. What "fail"? -- That is what is going on. People who thinks it makes no difference, default to the wife making all the practical purchases, and this is the secular result of the husband's being at work all the time earning and turning his paycheck over to her, and her spending it.