Of course! But, for temporary files, plain binary is extremely convenient. You produce temporary files in one program, use them in other programs, and delete them after all processings. Writing a plain binary is a one-liner and reading it as an mmapped array is a two-line code (plus using Mmap). There is no advantage in “a real file format” for this use.
In addition, some of my colleagues still produce plain binary files, which I sometimes have to use.
I agree! In our field, “netCDF” is the de facto standard and it’s so much better than plain binary. The problem is (or used to be) that its Fortran interface is so, so tedious to use that you are very reluctant to write a program to produce netCDF files in Fortran. I shrink from it.
Now that netCDF’s Python and Julia interfaces are so much better, there is no excuse to use plain binary, except as temporary files (see above), as long as you use Python or Julia. But, there are still Fortran-only people, even among young scientists, in our field . . .