It is always useful to know other languages.
Of course Fortran is not used widely anymore, but there are some specific areas that still use it, especially in physics and for supercomputers. It is a very good language for computations that need speed, because speed was what the language designers cared most from the beginning (btw FORTRAN's history is very interesting).
Also there are still people working on the language and the compilers. So it is not dead, it is just a language that settled in a niche.