History Lesson
The Tour could be seen as a demonstration of unity and strength. It is interesting to note that in the early years there was a part of France that this epic countrywide Tour could not include. France had lost Alsace-Lorraine to Germany and so if you look at the Tour maps from the first couple of years they simply avoided Alsace-Lorraine.
Complicity
However, by 1906 the Tour managed to sneak across the frontier and legend has it that the French riders would sing La Marseillaise as they rode through Alsace-Lorraine, encouraging spectators to do the same. This created a kind of French nationalist complicity.
Unity
In a sense, the Tour helped France by becoming part of the assertion of the country and an event that signified a sense of identity and pride amongst French people.
That's Culture Baby
The race is a major export for France and there is a huge amount of national pride surrounding the it. There is nothing as French as the Tour de France, so for anyone who wants to learn about France and French culture the Tour is a great way in.