Add to that the obscure gunmakers, Georges Granger, Henri Guichard and others built by French masters for the French customer to be used by the French sportsman in France and kept with in the family being handed down generation after generation. No wonder few have heard of them outside of France.
It's marketing, pure and simple. London was the centre of the British Empire and THE reason for the Empire was commerce. Raw goods from the colonies, finished goods to the colonies.
The French were not outward looking in the same way. They had a vibrant small arms industry and a vibrant small arms market, all within the confines of their borders. 950,000 Manufrance Robusts made. How many show up on our shores? Compare that number to the Parker, Fox, Ithaca, Smith and Remington production numbers. And that was just one model.
Its quite similar to the relative rarity of classic American SxS to be found currently in any part of Europe or England. Those guns were produced for the home market. Conversely in England, export markets, in particular America were a very important component of the business plan.
They are obscure to us. Probably not to French sportsmen.