Blowhard, Esq. writes:

It would be hard to imagine a more recognizable third place than a French bistro. Traditional third places tend to have physical features that unmistakably indicate what they are — these are sometimes called signal fittings. Thus, the American saloon had its swinging doors and brass spittoons, the English pub its beer pump handles and dart boards, and so on. The equipment that makes le bistro unmistakable consists of its outdoor wicker chairs, its small, marble-topped tables (about eighteen inches in diameter and pedestal based), and an overhead awning rolled up or down according to the angle and intensity of the sun’s rays. As these key visual elements protrude into the street, they as clearly bid the passerby welcome as they proclaim the place’s identity. Most of its customers do not really enter a bistro. By taking the preferred seating on the sidewalk, one remains as much out as in.

Bistros normally have no signs outside indicating their names, and for the best reason — most have no names. Naming something is the first step toward advertising it, and the French have always been admirably suspicious of advertising – only in recent years have they permitted it on television. But the major reason for not naming a bistro is simply that the neighborhood café doesn’t need a name. Its patron has filled a local niche and is content with his small, steady business. He has little interest in making his place a port of call to outsiders. The bistro belongs to everyone who lives in or happens by the neighborhood. It is as familiar to its regulars as one of the rooms of their apartments; its unmistakable and protruding presence into the street provides all the advertising that another enterprise might need. The no-name bistro also attests to the intense loyalty of its regular customers. The French are not pub crawlers or bar-hoppers, as are their English and American counterparts. A Frenchman has his place, and he confines himself almost exclusively to it. His place is referred to merely as le bistro, and when he tells his wife that he’s going to the café, she knows exactly where he may be found.

— Ray Oldenburg, The Great Good Place. Thanks to Lloyd for tipping me off about this book.