https://fr.wikipedia.org/wiki/Plan_d%27%C3%A9pargne_en_actions says:
Le PEA a été créé en 1992 afin d'encourager l'investissement en bourse des particuliers, notoirement bas en France.
The PEA was created in 1992 to encourage investment in the stock market [by] individuals, notoriously low in France.
Why did the French not invest much in the stock market prior to 1990?