Fortran is a more mathematical and formula based language

This would be my explanation of why Physicists would use Fortran. I remember when I first studied Fortran it reminded me a lot of learning Algebra several years before then. I think I was about in 7th or 8th Grade when I had Algebra and learning Fortran for me was a little like learning Algebra. And because Fortran is formula based it might make formulas (like E=MC2) easier to put into than other  computer languages in a useful way. This is my thought.