It may also have something to do with the availability of computers and software. It was very rare before about 1980 for people to have home computers that their kids could learn on. Before about 1970 it was rare for anyone outside a university or large business to get access to computers. There just were not as many programmers back in the day. Now you can't turn around and spit without hitting one.

It also could be simply a function of the demographics of HN readers.

Yes and Absolutely. (With the latter causing a good deal of the former.)