CAP FERRET, France — Pascal Rigo was just 7 when he fell in love with baking. Summering with his family here on the Atlantic coast, he began an apprenticeship in a small boulangerie, one of dozens that dotted Lège-Cap-Ferret, a spit of land about an hour’s drive southwest of Bordeaux.

Over the years, as he built a fortune in the baking business in the United States, one boulangerie after another closed until there was only one left in this tiny town at the tip of the peninsula where he has a home — a turn of events Mr. Rigo considers an affront to French baking.

His opinion of that bakery’s bread isn’t much higher. “People say the French are eating less bread because of gluten-free, because of low-carb,” Mr. Rigo said, sitting in a cafe here and dunking a flaky croissant into a hot chocolate made the French way, with melted chocolate diluted by warm milk. “But bread like that — that is the reason.”

All across France, the local boulangerie — the mom-and-pop shop that turns out classically crusty baguettes, eggy brioches, sturdy boules and croissants as light as air — has fallen into decline in recent decades as some people have adopted carbohydrate-free diets and others have grown accustomed to buying bread at supermarkets and convenience stores that make their own, using cheap ingredients. In the process, bread aficionados lament, the quality of the average loaf has plummeted, and many traditional bakeries have closed.