Why do You say "dear"

I understand this look polite “dear Mr …”
We often have to say that,to people who really aren’t dear for us,so why do We have to "play "
Why don’t We just say “Mr …” ?!

Social glue, my friend. Social glue.


if you really don’t want to say “dear” you could replace it with something else like: “hi” or “hello” or nothing, you could just write the person’s name. Although you should use “dear” if the letter is more formal or you are addressing someone you don’t know very well.