The problem is that Michigan's standards of "essential" items is different from other states. When you have many states falling under a federal standard which would be different, there will be complaints and lobbying to get their standards added. If cheese is not taxed, do you tax mac & cheese boxes? Potatos aren't, what about potato chips? See where this is heading?
I understand your concerns, and you make a valid point about the problems with varying standards in different states. In Michigan, all food is exempt, unless it is served in a restaurant.
To raise another point, the cheese in mac and cheese and the potatos in potato chips would be exempt anyway, because they are for business use. The business use exemption, while preventing the compounding of tax, requires that "business use" be defined and enforced. This creates a whole other set of problems.