There are dinosaurs such as I am who still operate in that environment you describe. I remember the Gulliver system, where unknown to those operating it, they were issuing native IMS commands without benefit of any meaningful interface. The problem has been one of market differentiation by means of ever more sophisticated mobile accessibility. This has created a competitive demand which rides roughshod over the traditional demands of zero downtime disciplines. As I say, I'm a dinosaur. Some of the macros called in my assembler are older than I am. The file open macros are sixty years old. They've survived for the simple reason that they have worked all that time.