It was my birthday the other day (45, thanks for asking). As usual, I received many cards from my friends and relatives in England, and absolutely none from the French. But as my wife has often remarked, the English send cards to mark just about every occasion (birth, marriage, new job, retirement, death) and every celebration, from Christmas to Hanukkah. The French, on the other hand, give gifts but disdain cards.
The question is - why? The answer is, of course, marketing. While Valentine's cards were handed around in Europe from the 15th century, the Americans turned greeting cards into an industry at the start of the 20th. It's no coincidence that the two biggest greetings cards companies in the world, American Greetings (founded 1906) and Hallmark Cards (founded 1910) are both based in the US, as is the Greeting Card Association. This trio promoted greeting cards as the ideal media with which to communicate your feelings to people you cared about. And as these feelings were generally expressed in English, by American copywriters, they caught on in the UK too. The marketing push clearly didn't achieve much success in France.
Today, e-cards and greetings via Facebook are slowly replacing the paper variety. Which is a shame, because there's nothing nicer than receiving something in the mail that isn't a bill. Especially on your birthday.