Well, nobody else has bitten this hook, so I'll give it a try. Germans generally speak excellent English, so having their site in German is just a friendly gesture, a bit like the way we say Boro Da to the Welsh when they burn out holiday homes. You may like this video, especially the first 30 seconds:
https://youtu.be/hW28HSSfEg0 -- there's subtitles in German AND English.
The French, hmmm, the French really don't like speaking English. And we only speak to them in a joke accent, e.g. Boris or Churchill. So the French site is in English to remind them that English is the common language of the EU and they need to suck it up.
Canada? I've no idea. I'm surprised that in recent weeks the whole of Canada hasn't elected to speak French exclusively. While raising 'le middle digit' to DJT.
I won't claim these theories are well researched. Probably someone else has a better explanation?