In a sense, you kind of ARE their boss. All of the people you describe calling you “Boss” were in service positions. You were a customer, so kind of the whole reason their job exists. Beyond that, I think it’s a variation on “sir” and other forms of impersonal address.
Sorry about that. Won’t happen again, massa.
Hope I’m not being racist here (really, I don’t INTEND to be!), but I’ve noticed that people from India, Pakistan, and that general region seem (at least in media) to call everyone “my friend” if, say, you go into a store they work in or you’re working with them.
Actually, here in Tucson, I do hear the word “jefé” a lot.
Great Caesar’s Ghost! Don’t call me “chief!”
When I was in the military, where any idiot with a bachelors in teaching woodshop to highschoolers might be in command, we called the people we respected boss, so suck it up.
But are you “Like a Boss” ?
For whatever reason I am in the habit of addressing agents of merchants and service companies as “you guys” so I might ask “do you guys carry start relays?”.
I’ve had maaaaybe four women over the decades who freeze up on it and go I’m not a guy.
Another anec-data point: The only people I can think of who typically call me boss outrank me. One of them gives off a bit of a sun-bleached surfer dude vibe, great guy to work with, even if I never sense that we’re thinking in the same direction.
I’ve met the odd person who took offense to being called “Sir”, particularly a few of them when I was in Basic (no, not the instructors, we were actually required to call them “Sir”). I tend to tack it onto my sentences as a verbal tic, so I never really intend any disrespect. That said, if I am talking to someone that I know should be addressed differently (such as Army NCOs), I’ll make a point of using the proper title. In the case of the Army guys, I even make sure to slur it properly (“Sure thing, Sa’rnt!”).
Okay, you’re not my boss. Got it, coach.
Listen, Chief, you’re hardly being a constructive force in this discussion. 
Won’t happen again, dickface.
This, ace.
Is that your dirt in boss’s hole?
Maybe it is a better way of saying ‘sir’.
I wonder if the same term could be applied to a woman.
Or would it be ‘boss lady’?
And would the woman feel offended or complimented?
Consider yourself lucky. My dad had a bunch of Hispanic employees, and they all called him “Viejo.” Literally “Old Man.”
I seem to notice the “boss” thing mostly around people who tend to be blue color. When I was doing some manual labor in college, pretty much everyone I worked with would refer to me or others as “boss”. It seems to me to just be a slightly more slanged version of “sir” but not quite as slang as “dude”. I get the idea, that it’s intended to be sort of respectful, but frankly, it is something that has always kind of bothered me since I really don’t see people in a hierarchy and I feel like it sort of feel like anyone calling someone boss, especially outside of an employer/employee relationship has a way of falsely creating that sort of hierarchy and I just want to relate to people as equals, and it bothers me just as much when people see themselves as less than me as when people see themselves as better.
Smurfs?
I’ve called my manager boss lady before, drama has failed to ensue.
B&D Smurfs, now there’s a vivid image.
More often than not, it’s not intended to be “respectful”. It’s intended to demonstrate an inappropriate level of familiarity and casualness. Do you think any boss wants their employees calling their customers “boss”, “chief”, “pal”, “bro”, “man”, “friend”, or “buddy”?
No problem…GAYLORD!