Why does Everyone Call me Sir?

I was walking to work this morning when a gentleman from my church pulled up to ask me if I wanted a ride. I politely said "no thank you," and he said "Alright sir, have a good day," and I almost missed a step. I should have been calling this man 'sir' because he was my elder, not the other way around. Then I got to thinking; lots of people have called me sir, and it was becoming a little unnerving. My friends did back in dorm, but we often made a game of using unnecessary formality because it was 'classy.' I referred to my friend Josh as 'Dr. Knowles' and my other friend Kevin as 'Dr. Reid' and we always referred to the other as 'sir,' as if we were long time academic colleagues (probably inspired by a common love of C.S.Lewis). Some of my friends continued this past that year but I never thought much of it. But when people I don't know begin to call me 'sir' I can't think of it in the same way. I don't mind the formality I'm just unsure why people seem to think it necessary. It normally isn't an issue at all, but when my professors, my boss, my pastor, the registrar, dean, and president of the school I work for call me 'sir' almost unconsciously it becomes unnerving.

I don't think I radiate a presence that inspires that sort of respect or formality. I'm tall, maybe even good looking, but an often unshaven beard, a frustratingly unruly head of hair, and outdated glasses should reduce me to 'average Joe' status I would think. Is it the way I hold myself? Is it because I try to be polite and formal myself; looking people in the eye, listening, and respecting them in my speech and actions? If so, then my goodness, there is definitely something to be said for how one holds himself.

The problem is that I don't see myself as worthy of that level of respect, not from my elders, and certainly not from those who hold authority over me. Without a relationship that gives the formal 'sir' a context I'm not sure how to interpret it. Among peers it has been a classy display of friendship and comradery which I will share with them gratefully. I don't have a context for when someone I do not have a friendship with calls me 'sir' or when that person happens to be the people who I work for. Then I begin to wonder... was friendship and comradery all that my friends were trying to communicate... and I suddenly become a little frightened.

Who do people see me as; really? Who am I; really...