Why are people so bad at budgeting their money? ?

I know so many people that are always complaining about how they don't have any money, but then you find out how they spend their money and immediately know why. So many unnecessary expenses and not trying to live within their means. If they lived somewhere they could actually afford, learned to shop for groceries and cook at home instead of going out all the time, stopped spending so much on alcohol, cigarettes, and drugs, and stopped spending on things they don't actually need such as big TVs, expensive cars, etc, they could actually live quite comfortably. Why isn't budget management taught in schools?