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.
I'm only pointing out that ever since the French revolution, we have a rich history of regime change (and also of strikes and demonstrations). Some were due to external factors (like the Vichy régime during WW2) and some were bloodless (like the end of the Fourth Republic).
Us rolling the dice whenever we have a major political crisis is a meme at this point, for better or for worse we're just not the kind of people to keep the same constitution around for 250 years.
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.