The Hamlet Project

In my edition, Reynaldo is listed as Polonius’ “man” which might indicate a valet or a servant of some kind but not specifically.
I have questions about this – because why is Polonius calling his servant “sir”?
Sirrah, okay, that’s a servant, sure – but sir?
Sir, would seem to me to be a title among equals or betters.
Granted, I am not an expert in titles. I have not closely examined who calls who sir throughout the canon but every example that comes immediately to mind fall in the category of equals.
“Do you quarrel, sir?”
“Quarrel, sir, no sir.”
A couple of ruffians and servants, sure – but equals.
Rosalind to Orlando: “Sir, you have wrestled well.”
Equals.
I don’t know – Sir shows up a LOT in the plays. A LOT.
Who’s got the numbers and statuses?