Well, Japanese also has 5 levels, and as mentioned above, it’s difficult. I mentioned to my wife I had learned that husband says “kimi” to wife, but wife says “anata” to husband. Her response was along the lines that if I tried anything of the sort I would be in pain.
Anyway, Swedish has “ni” as the formal version and “tu” as the informal, and it’s not nearly as strict as what Spiny Norman described for Danish. In Swedish you can quite happily call your boss “du”. “Ni” is more marked as showing respect to older people or strangers you’re meeting for the first time. Actually you could quite easily insult someone by saying “ni”.
All of which is to say to the OP that it varies strongly from one language to another and I guess this reflects the culture to some extent.