Technologies that endure
After almost 50 years in the field, the initial impetus to revisit old technology is a mix of nostalgia and curiosity.
The University town where I first encountered the magical world of computers had a well-equipped computer center. Most of the equipment was shared among the faculties of the university and few scientific and agricultural interests in the neighboring companies. Today all this beautiful equipment has found its way to various technology museums and probably to the metal recycler or the landfill.
Computer Sciences and the Computer Industry has made so much progress in these fifty years that the sheer volume of innovation and change is hard to fathom.
There is quite a large crowd of people who are interest in the technology of yore, reviving a demand for experts in this field.
For example, COBOL:
The requirement for COBOL knowledge has never disappeared. While it was thought that most COBOL programmers have either passed away or retired, the language has remained, although more discreetly, hidden behind the new technologies and buzz words of every day.