The top consumer and ambassador of French wine steadfastly remains the Englishman (or woman!). Always faithful, despite the differences that might set them against their touchy neighbours, the English have been able to exert their influence over the content of their favourite tipple by imposing their own norms on it. If today’s, and indeed yesterday’s, bottle of wine contains only 750 ml, that’s because France’s oldest and best “enemy”, for reasons of pure accountancy, demanded that their “gallon-based” measuring system be the only reference when bottling the most famous and prestigious drinkable element of French gastronomic heritage.
So, all those “one of our quirks” stories to explain this “peculiarity” must be forgotten… The moral of the story: the customer is always right, that’s all there is to it.