In a general push for removing Microsoft, Google and any US or other non-EU dependency, the French government has been rapidly creating an open source set of productivity tools called “LaSuite”, in collaboration with the Netherlands & Germany.
LaSuite is allegedly being developed using Django.
https://lasuite.numerique.gouv.fr/
Good question. I guess is because they want to have full control over the project, since is a gubernamental thing. But at least using LibreOffice as base for it would make all the sense.