I am going to focus on
Is this an age, or more of an era issue? We don't still, or the upper classes don't still say this do they?
It never was a social class thing. And yes it is still done today.
First thing to realize is that the US population in 1912 was about 95 million. Today that's about the size of three states(Texas, Florida, and California).
Second is that, with everyone so spread out, it was not uncommon to have one or two family lines dominating an area. This had nothing to do with income or wealth. It's just a fact. As A Husband and wife settled in Backwater Arkansas, they had kids, their kinds had kids, and so on, till a large part of the population of Backwater was a single family. That family didn't have to be rich, just prolific.
Third, when people left their family lands and moved elsewhere they looked for people they recognized. It was not uncommon, to run into someone from your home town, that was part of one of the larger families. Hey, John Smith, from Backwater, Your not related to the Backwater Smiths are you? Oh your Jane's second cousin on her Dad's uncles side? Oh yeah, I think we shopped at the same grocery store that one time, lets be friends in this big scary city where we don't know anyone.
Finally, back then, but even now, travel was a big deal. You couldn't catch a flight to so an so. So if your blimp was leaving out of Backwater Arkansas, then a lot of the people on board would be from backwater and the srounding area. People would travel for a few days or a week or two to get something big like the Titanic, but that still limited the area to basically New England. Remember if you traveled to New York, you were probably there for something else, the Titanic was likely just a fresh new way to get to where you needed to go. It would be unlikely to travel from California, to New York, just for the sole purpose of taking this one boat. Maybe you timed your trip around it, but you probably didn't travel there the same way we travel across country to take a cruise ship now.
So today, this still happens. I get this all the time. When someone finds out my Family name and that my family was from Hastings Michigan, I get a question very much to that effect.
You would be surprised how many people you run into that know some cousin that you barely know by name only, that one time you tried to look something up on ancestery.com.
Keep in mind that not everyone has their eyes glued to their cellphone screen and facebook at el. Some people actually do talk to strangers. And this will come up frequently, if your in an area with a lot of people that travel from other areas.