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.