France has a more diverse culture than many other parts of Europe have. The culture has been shaped largely by geography for one thing. It has also been very welcoming of different ethnic groups and has not bothered to be strict on doccumentation of such.
High culture has been a part of France since the 17th century, especially in the city of Paris. Employers in France, in general, hire foreign people freely which is a huge reason the country is diversified. Some of it's welcoming of other cultures has gotten it into trouble but for the most part, it is thought of as very nice that they let just about anyone in.