Do French intellectuals take part in left-wing politics less often than their counterparts in other rich nations? I don't think so (but you may have comparative worths of respective intellectual productions in mind -- in that case, I'd say globalization has exercised a homogenizing influence).
For better or worse, France has fostered the idea of politically committed public intellectuals, from Zola to Sartre to Foucault to beyond. In contrast, we have soundbites from experts in think tanks.
Yoshie