I have been at various times an engineer, an optical designer, a mathematician, and a physicist. I am now retired, but continue to be interested in optics, physics, and mathematics.
I have been using Mathematica since Version 2.1. While I have specialized tools for optical design and finite element analysis, Mathematica is my Swiss Army Knife. I use it for theory, modeling, data reduction and analysis, graphics, . . . . The only thing I can't do with it is remove wallpaper. That still requires a steamer.