I'd suspect that TeX is mostly used in academic departments where UNIX has been the de facto operating environment for a long time (e.g. engineering, computer s

I'd suspect that TeX is mostly used in academic departments where UNIX has been the de facto operating environment for a long time (e.g. engineering, computer science, mathematics, physics) and there is a well-established "command line" culture. In more Windows-centric departments, MS Word is ubiquitous. If the Equation Editor functionality in Word isn't sufficient to do what you need, then MathType (the professional version, sold separately) is generally adequate to get the job done. If you need more control than what MS Word can offer, then you generally go with InDesign instead.