I think it’s also a question of safety. Speaking the same language (here it should be english) helps all pilots to have a better picture of what is going on around them. Sticking to your own national language doesn‘t help anybody, au contraire, it is rude and sounds arrogant.
Flying helicopters I don‘t get around that much in Europe but my experience is:
Scandinavia: they all speak English automatically and thus sound very friendly
Benelux: same here
France: they simply don‘t want to speak English though they could. Everytime I fly to France I make bad experience. They simply ignore you on the radio and for sure you get parked at the end of the world. Maybe it’s because of our history.
Czech Republic: same as Scandinavia
Poland
rofessional and strict, sometimes hard to understand