Think of all the things you can buy in the city. Better yet, think of one. A cup of coffee, say. You buy the coffee itself — a portion of the grounds, use of the filter, and momentary rental of the machine that brews it. You purchase the cup, a plastic lid, and maybe a cardboard sleeve to protect your hands. Using a plastic stirrer, you might add cream, whole milk, skim milk, soy milk, real sugar, synthetic sugar, or another sweetener. You’ll probably need a napkin, too. All these items, of course, must be at the coffee shop before you are. Which brings us to the delivery trucks, those hulking, noisy things that prowl Boston’s narrow streets every day to meet consumers’ fickle demands. I was listening one morning on Beach Street in Chinatown, where a small group with dollies briskly unloaded cake boxes and bread bags, fresh off the boat from China and destined for a nearby bakery. This was all going fine until a city parking enforcement officer approached with a bark: “Move that truck outta here!” In this cat-and-mouse game, it was easy to have sympathy for the driver. This was Chinatown. There was nowhere else to park.