I’m sure Professor @Triedaq is correct in his memory of the automatic transmission. I guess for me it was mainly around 1956 when I saw a few, even though there was a Buick and Caddy with one in the neighborhood. So really that would mean people born in 1940 would have been the first ones to drive one. But they weren’t old enough to buy them. That would have been older people or the “greatest generation” back from the war. But automatics like air conditioning and power steering and brakes were at extra cost and a lot of people didn’t want to pay the extra $400 or so for an automatic. So it really wasn’t until the 60’s or later that these features became more standard and pretty much what was on the lot. My first two cars were manuals and my first automatic was about 1969.
I really don’t think it had anything to do with how people were raised. It was just what became popular and standard, like TVs. Farm kids were exposed to manuals and many city kids also if that was what was around. After watching a video though of a kid trying to open a can for Thanksgiving dinner with a manual can opener and couldn’t figure it out, I’m going to make sure my grand kids at least know how to open a can without a pop top. I mean what do you do if the power goes out and the electric can opener doesn’t work? Can result in death or severe discomfort.