Fortran still dominates certain areas of scientific computing / HPC, primarily computational chemistry and CFD. - https://fortran-lang.org/packages/scientific - you don't hear about most of them because they're generally run on HPC centers by scientists in niche fields. But you do get their benefit if you buy things that have the chemical sector in their supply chain.
The common thread is generally historical codes with a lot of matrix math. Fortran has some pretty great syntax for arrays and their operations. And the for-loop parallelization syntax in parallel compilers (like openmp) is also easy to use. The language can even enforce function purity for you, which removes some of the foot guns from parallel code that you get in other languages.
The kinds of problems those packages solve tend to bottleneck at matrix math, so it's not surprising a language that is very ergonomic for vector math found use there.
Same for Matlab, it's mostly used by niche fields and engineers who work on physical objects (chemical, mechanical, etc). Their marketing strategy is to give discounts to universities to encourage classes that use them. Like Fortran, it has good syntax for matrix operations. Plus it has a legitimately strong standard library. Great for students who aren't programmers and who don't want to be programmers. They then only know this language and ask their future employer for a license. If you don't interact with a lot of engineers at many companies, you aren't going to see Matlab.