Because Britons are cowed by generations of monarchism to listen to authority. The French question that authority in a way that terrifies the British.

I think my experience in the United States broadly supports Ms Sayers' thesis. Our revolutionary origins are taught extensively in schools, and you can't be outside in the US for more than ten minutes without encountering some reminder of the American Revolution, but my exposure to political philosophy was basically nonexistent until a single semester my senior year of high school, and even then was pretty scant. As such, we have a very robust culture of protesting, but it is highly ritualistic and not very effective -- there's ongoing protests that have been meeting weekly or monthly for decades in the same government-approved spots on the same government-approved schedule because we're aware that protest is necessary, but we have no sense of the political theory that underpins what would make protest effective. Our education has half of the difference Ms Sayers identifies between the UK and France, and our protest culture is located somewhere in between them.

In the final year of lycée, pupils study Rousseau’s Du Contrat Social (The Social Contract), which argues that citizens should only surrender their unrestricted natural liberty in exchange for civil and moral freedoms. You give up your individual interests for the volonté générale (general will) – put simply, you pay heavy taxes and in return you expect the country to work. That bargain is how the French understand their relationship with the state. When the government raises the retirement age, lets electricity bills soar or cuts school budgets, that is seen as a breach of the social contract. Protest is the automatic response.