>>2208990Keigo. English-speakers use familiar language to come off as friendly and welcoming. Japanese speakers stand on strict formality out of fear of coming off as disrespectful.
Generally speaking, the person being addressed respectfully will give their interlocutor permission to use more familiar language, but the ENs don't know enough about japanese to understand that they have to be the ones to do that.
This is what made Ame calling Aqua "Onion" so funny. It was completely rude to the japanese, and came off as rude, but they can't actually tell if Ame meant to be rude and that's just an american thing or if it's just a cultural misunderstanding. The confusion made it hilarious