That's literally the difference: this isn't word processing, it's typesetting. If you want word processing, use a word processor, and trust it to make the right choices for you. However, if you've spent any amount of time actually trying to get those images placed correctly, or those page dimensions perfect, word processors fall short and your only other option is a TeX engine, or typesetting applications like InDesign. Of those two, one category is free, and the other costs $50 a month these days.
Certainly this is the case when you need to typeset maths, but even when you want proper typesetting control over something as "simple" as mixing English and vertically typeset Japanese, Word and friends are insanely ill-equipped to do what you need them to do, whereas a modern TeX system like LuaTeX or XeLaTeX will actually let you define what you need and then get out of your way from that moment on.
> if you've spent any amount of time actually trying to get those images placed correctly
I had to learn LaTeX as part of my education, and as much as I like it this is one of it's weaknesses, not it's strengths. I saw my fellow students struggle to get all the images on the pages they wanted, and if they asked for help the answer was "Let LaTeX decide where to put it".
Don't get me wrong, I still love LaTeX. It let's me:
* Keep a whole document in a consistent style I can change at any point in the process.
* Produce pretty mathematical formulas and proper justified text.
* focus on writing instead of fiddling with where images go (I let LaTeX decide, it's usually pretty smart about this)
* Write code that writes part of my document. I used to write code to do the boring parts of certain proofs, and it would produce the LaTeX for me.
Certainly this is the case when you need to typeset maths, but even when you want proper typesetting control over something as "simple" as mixing English and vertically typeset Japanese, Word and friends are insanely ill-equipped to do what you need them to do, whereas a modern TeX system like LuaTeX or XeLaTeX will actually let you define what you need and then get out of your way from that moment on.