As opposed to your genius financial management skills where you unnecessarily fail to take advantage of the fact that you can come out way ahead on per diem and put it to use in other areas of your household budget.

I think you are confusing the issue here. No one is saying that per diem should replace income and that seems to be the conclusion that you assume we are jumping to. Per diem should never replace income but when per diem rates allow us to come out ahead than there is nothing wrong with that extra money being used for other purpose such as paying off student loans or an Xmas/Vacation fund.