From anecdotal evidence I will put forward another theory. Because CS and programming are relatively new and rapidly growing fields a large number of programmers in the early years were random office workers who could type, press ganged into development duties. Education started to catch up in the 80s and 90s so young kids with a real grounding in fundamentals were coming into organizations staffed with older developers who didn't have a clue. On average, older developers were incompetent, not because they were older, but because they were less likely to a) have any formal education in what they were doing and b) a particular interest in what they were doing besides the paycheck.
I can't comment about middle America banking, but this was definitely NOT the case in Silicon Valley. People who became programmers were extremely bright and a very diverse lot. A significant number were accomplished musicians. A lot from mathematics and engineering. I even worked with a guy who dropped out of physics because programming was personally more rewarding than being yet another post-doc at Fermi Lab. My associates didnt learn CS, they invented it. (OK a bit of hyperbole there, but that was what the times were like.)
One might also say there was far less information available at their fingertips to help them learn, even if they wanted to. They may have been relegated to one or two books, which likely were outdated or wrong.
I agree and commented as much on the thread. People started playing with these things in the 1950s, 1960s etc but the market for software developers really started in the 70s, 80s, 90s, so you saw a disproportionate amount of younger developers in this field.
Just like with radio in the early 1900s and other new industries. With time that bulk of age averages out to other industries. Development is an important role in all that we do now, why would only 20yr olds be doing it.
