Re: Why COBOL?
I can remember working at a client in the 80s, where we were allowed 2 compiles per DAY! This is the sort of limitation that encourages just the mindset and rigour you describe. I will admit to having written programs of several thousand lines that (s) compiled first time and (b) passed testing first time. We cared back then about what we wrote because the systems we wrote were the systems that WERE the company. Not surprisingly, many decades later, these systems, the legacy systems, are still the systems that decide if the company does business tomorrow.
As an afterthought, in Michael Lewis's book Flashboys IIRC, quite a bit of the story partially revolves about "Russian programmers" and why they are so well respected. It seems they would have all been excellent COBOL programmers, as planning, rigour, structure etc. are part of their skill set.
Which reminds me of Lewis's first book, Liar's Poker, which took place just down the corridor from my office at Goldman Sachs. At the time (1986) we were establishing the very basis for the GFC of 2008 and the entire system was written in --> FORTRAN. We had no Russians, but we really sweated the details and performance of the instrument valuation calculations.