they are not berets they are actually called lid golf hats for men here, in paris, they wear them because they are stylish, you know paris, all about the style
The beret is traditionally an item of male headgear. It was originally worn by Basque fishermen. It was later adopted by many military units (particularly paratroops). By World War 2 it was the most common headgear worn by French peasants so was adopted by the French resistance members both male and female.