When you work with the general public you become aware of trends that you would probably never notice. For example I noticed that during the years 1994-97, most young, male, middle-class customers ended a transaction by saying 'Bye now', as if they were presenting a television programme for young children. Then it suddenly stopped for no discernible reason. Looking back, the only two events of 1997 were Tony Blair and Princess Diana. Perhaps they'd OD'd on touchyfeelyness and felt a need to get back in touch with their inner Conservative. I don't know.
Another example is from about eight years ago, when several people I knew started saying 'Blahdiblah'. I'd never heard anyone say the phrase outside New York, but suddenly it became the default option for anyone who wanted to cut a sentence short. I waited patiently and sure enough, it suddenly disappeared without a trace after a couple of years.
I also recall when AQI (Australian Questioning Intonation) suddenly appeared out of nowhere. One day my wife came home from work and everything she said sounded like a question. It was bloody annoying, but she wasn't even aware of it. Somebody new had arrived in her office and their speech inflections passed around like a virus. I'm acutely aware of accents, probably because I grew-up in a working-class family and changed my accent in my teens, but my wife rarely notices how people speak.
I remember Orwell writing about his days as a tramp and noting his surprise at how many fellow vagrants failed to notice his Eton accent. Orwell concluded that some people aren't attuned to oral idiosyncrasies and are more likely to judge by appearance.
Several years ago I read something by Chomsky about this and it was a huge relief to find that I wasn't in some 'Invasion of the Body Snatchers' scenario. Chomsky argued that language works like a virus, inveigling its way into the collective subconsciousness and I'm sure that anyone who works with the public and is attuned to accents will have noticed this phenomenon.
If you haven't, you probably think I'm completely barmy.