Why does grinding the meat at home make a huge difference vs grinding it in a factory? Depending on the cut you choose, the condiments you add, and the portion size, a hamburger at home could be Lot less healthy than a McDonald’s burger. McDonald’s patties don’t have any fillers afaict.

The point is that “junk food” is a pretty amorphous and vague category. If you want to enforce portion or calorie restrictions you can do that, but it would have to be way more encompassing of a regulation than targeting “junk food”