It can also vary some companies try and have a first name policy for internal use. To try and create a less formal atmosphere. So in theory if the head of the company came to visit your location they would be addressed by their first name.
Ah, but in certain settings (at least here), you do introduce yourself as Mr or Ms Smith. When I worked in corrections, we didn't allow the inmates to use our first names, so we rarely said them ourselves. "Hi, I'm Ms Smith. I'm going to be your case manager."
This actually happens in my field of work. The director of the institute and the last PhD candidate both address each other by first name. I think this is pretty widespread in academia, but by no means universal. You are, of course, entirely correct. When we discussed the issue of titles previously, I added a caveats for people using them out of professional needs (I used the example of police officers, but of course it works for correction officials, military personnel, physicians, etc). It just emphasizes the silliness of arguing for a one-size-fits-all politeness.
A lot of this comes down to politeness vs. friendliness. They are not the same thing, and I think modern culture increasingly values the latter over the former. After I got out of the military, I actually found it pretty refreshing to use first names with my coworkers. but I still find it presumptuous and overly familiar when complete strangers address me that way.
I have to admit I find it a little odd to be called by my first name by someone who I've never met. It is especially annoying to me because I go by my middle name so it sounds really weird when someone calls me John. On the other hand, I have no problem being called Andrew at my local comic book shop, but I am a regular there and they know me. As to referring to your elders as Mr. or Mrs., that was certainly the case when I was a kid growing up but it is not something that has carried over into my adulthood. I always introduce myself as Andrew to children and don't expect them to refer to me as Mr. or Sir.
Perhaps, it is more true in the South (US), here we address elders as Mr. or Ms. So-and-so. Children of my friends call me Mr. [First Name]. It denotes both familiarity and respect. I shall take your challenge. Addressing an elder as Mr. or Ms. So-and-so displays a respect for, not only their age, but their life experiences. They have lived longer and experienced much more than a younger person. Elders often have wisdom which comes from trial and error in their earlier years. Listening to them, and respecting them, can often save a younger person much heartache and pain. Sadly, younger people do not often take the time to learn from their elders.
^Some old people are assholes. I respect people for who they are, not for their age. My default position to any person is one of respect, however, being older than me has nothing to do with that -- being a person, old, young, or a peer is all that matters.
Lived longer; yes. Experienced much more; usually, but not always. There are thirty year olds who have lived more harrowing, dramatic, fulfilling, varied, successful, traumatic, romantic, well-traveled lives than some seventy year olds. It depends on the person, and you have little or no way of knowing what their lives have been on introduction to a stranger alone. So again, you're essentially asking someone for additional respect simply by having lived longer, not by the content of your character. Yep, that is often true. Also often true is that elders have offensive beliefs and standards which they've rigidly held on to out of tradition or upbringing despite being well past their "sell by" date in modern society. Often those beliefs manifest in oppressing minority groups through political action, a process which sometimes drags on longer than it should as people live longer these days. Maybe if people didn't just automatically assume that that flow of wisdom should only go one way because older people are better by default they'd learn a thing or two from (some) younger people about tolerance for others, and we'd hopefully live in a better world. Now, that's not a blanket statement either way. There are young people who are rigid and intolerant, and old people who are open minded and tolerant. Again, it depends on the person, which is why you shouldn't assume. You should listen to and respect anyone in equal measure until they give you a reason to do otherwise. Or if they're infants. Screw them. Greedy little nonsense babbling bastards. It's always "me!, me!, me!" And you base that on...? Is there a study in Nature or Scientific American about the Older People/Younger People learning ratio being in decline? To quote my esteemed elder Samuel L. Jackson from his career defining performance in the heartwarming Christmas classic, The Long Kiss Goodnight: "When you make an assumption, you make an ass out of u and mption."
I've worked with hundreds of children over the past 10 years, and one of the greatest lessons I've learned is that the ratio of wisdom to idiocy doesn't really change as people age.
I love "Mr/Ms Firstname". Less formal than the way I was raised (further north) to call adults Mr/Ms Lastname, or occasionally Mr/Ms L if I knew them well. But not as informal as just first names. I have to admit, I'm not comfortable when someone I'm not close to tells their, say, three-year-old to call me Firstname. Sometimes I let it go; sometimes I tell them it's Ms. Firstname, please.
^ Wouldn't it get a bit boring, calling everybody Mr./Mrs. Firstname or Lastname? (badump bump, TISH)
Whenever I'm riding in the backseat of a car, I expect, nay, demand, that whoever is driving address me as "Ms. Daisy" as a sign of respect.
In my experience, that ratio does change. Unfortunately it moves closer to 1:3 and not the other way around.