I have noticed that many notable Americans, most recently Trump, Obama and Stephen Colbert, often address their audiences as folks. This sounds like an attempt to sound down to earth and persons of the people though I realise Americans may have a different perception and not even notice it. Professors in lectures would never use folks. I remember Ross Perot repeatedly addressing a black crowd as ‘you people’ which didn’t go down at all well. Would ‘you folks’ have worked? It also means parents (family?) as in Ted Cruz’s ‘My folks brought me up a God-fearin’ Christian’.
I can’t remember hearing it in Britain. There is a Kingsley Amis novel called The Folks That Live on the Hill so it has clearly fallen out of use. In the 1959 novel Billy Liar, Billy’s mum refers to her husband and herself as ‘ordinary folk’ and I also recall hearing or reading ‘simple folk’ somewhere. I was a middle class boy and wouldn’t really know.
That’s all, you people!