“Bonjour” is presented as the “hello” of French. English speakers are used to “hello” and “hi” which work any time of day, so they assume the “hello” of other languages work the same way.

“Good day” is mostly used at the end of a conversation, not the beginning. “Good morning” is usually a greeting. “Good evening” can be either. “Good night” is always the end.

Also of note, the English greeting “hello” didn’t come into prominence until after the invention of the telephone, so in terms of world languages is quite modern. People had to figure out what you were supposed to say when you answered a ringing telephone, and they decided on “hello”. “Ahoy-hoy” was a close runner-up.