Disclaimer : I am from India.
People here(India) write "dear" "sir" "dear sir" a lot and here's why...
We are 7 billion people, out of them only a few millions of them get English education till high school.(well English is not our official language as people think it is, I can't even keep track how many languages I have heard)
We in schools are taught to write letters to dean, offices, boss, mother, friends etc.
So we usually start letters to Dean, offices, boss by calling them Sir or mam, or dear sir/mam.
And dear to mom, friends etc.
Most indians only study English till high school or first year in college.
So, it's coded in them to call people in business "sir/mam" and "dear" and "respectfully sir" etc.
Don't take it as offense, just tell them of you don't like to be addressed by dear etc
Name calling is not really a thing here...
So this stuff happens

