In response to the NYC ban on trans fats, Ampersand noted, “Banning trans fats in restaurants, but not in grocery stores, doesn’t make sense. I guess the supermarket lobby is more powerful than the fast-food and donut lobby.” The Economist’s blog takes on the question:
I’d guess that it has more to do with public choice theory than ardent lobbying. Since national food producers are unlikely to reformulate their entire line for the benefit of a few million New Yorkers, a trans-fat ban would sweep large categories of food off the supermarket shelves, in a way that would be directly and obviously attributable to the ban (since they would disappear from every supermarket shelf at once). Banning them in restraurants, on the other hand, will merely make some of the food taste worse, other of the food more expensive, and so forth, in a thoroughly idiosyncratic way. Consumers are unlikely to connect thousands of subtles shift in their local restaurant fare to the ban, as they surely would of glazed donut holes suddenly vanished from the shelves of the city. The legislators do not need to be paid to act in their own self interest.
Although for me, this answer suggests Marx (on obscured casual pathways as a mechanism in ideology, here, with causes attributed not to inputs but to other factors) as much as it does public choice, which is not to say that the answer is correct.