> A grocery store shortens the time to buy food and so on. a non-patron of the store still incurs the externalized cost of a store (such as increased traffic,

> A grocery store shortens the time to buy food and so on. a non-patron of the store still incurs the externalized cost of a store (such as increased traffic, noise, etc). A patron of said store has benefits which offsets those externalized costs, but not for the non-patrons.