Probably because we have a well established history of regularly changing regimes. Since we overthrew royalty in 1789 we've had five republics, two empires, three monarchies and a bunch of short-lived totalitarian regimes, coups and other major political events.

If anything, the longevity of the Fifth Republic is starting to become unusual (only the Third Republic and the Ancien Régime have lasted longer). Maybe we're overdue to flip the table again as per tradition.