Isn't it obvious? Because the ChatGPT output wouldn't be reviewed!
You buy books like these exactly because they are written by a professional, who has taken the time to divide it up into easily digestible chunks which form a coherent narrative, with runnable intermediate stages in-between.
For example, I expect a raytracing project to start with simple ray casting of single-color objects. After that it can add things like lights and Blinn-Phong shading, progress with Whitted-style recursive raytracing for the shiny reflections and transparent objects, then progress to modern path tracing with things like BRDFs, and end up with BVHs to make it not horribly slow.
You can stop at any point and still end up with a functional raytracer, and the added value of each step is immediately obvious to the reader. There's just no way in hell ChatGPT at its current level is going to guide you flawlessly through all of that if you start with a simple "I want to build a raytracer" prompt!
I canceled my book deal
https://austinhenley.com/blog/canceledbookdeal.html