Lee Phillips, ars technica, Scientific computing’s future: Can any coding language top a 1950s behemoth? here. This is just not that hard to explain. Must be something else going on here.
In the 60 years since the creation of the first Fortran compiler, there has been tremendous activity in the field of programming languages and computer science. Entire paradigms of language design and program organization have arisen and done battle with each other. Fortran has remained serenely detached, now and then incorporating an idea or two into a new version of the language.
While structured programming, object orientation, functional programming, and logic programming all arose to solve various problems that supposedly were not solved by primitive Fortran, none of the languages that embodied these new organizing principles came close to supplanting Fortran in the realm for which it was invented: scientific and numerical computing. This remains true up to the present, as shown by the examples above and by the content of courses and textbooks on the subject. Introduction to High Performance Computing for Scientists and Engineers, for example (published in 2010), contains most of its code samples in Fortran.