Somewhat related, the partial-illusion of "where did all the old developers go, they seem way too rare, something is happening to them." While attrition and ageism do exist, there's a bigger factor.

The total workforce has expanded dramatically over time, so even if everybody in the started-40-years-ago cohort remained alive and employed, those (now much older) people would still be a tiny minority among the bigger and bigger cohorts that kept joining since then.