> It must be on purpose, a big f-u to non native French speakers.
I hate this stupid stereotype that French people don't want to learn/use English because they're too proud to do so. I've heard this countless times.
Truth is English isn't an easy language to master for native French speakers. It's similar for Italians or Spaniards for instance. And conversely, nobody expect americans or brits to be fluent in a foreign language.
As for institutions websites, I agree with you it's a shame they don't offer an English version more systematically. I just checked and it seems "impots.gouv.fr" (tax website) doesn't have an English translation (research and educational institutions always have one though).
I don't know why it is not the case. Maybe there's some truth in what you're saying. Some people may think it's not worth the cost since foreigners willing to live and work there should learn the language eventually. I disagree with this type of nationalistic ideology, but again, it's certainly not unique to France.
In any case, I think things are improving. For instance, more and more universities have English curricula nowadays.