"Writers don't write because they can write. They write because they can't not write."
Writing is an incredibly important communication skill, and it is a forcing function for understanding a topic. But still, writing a book is rarely the best use of your time nor the best way to learn to communicate or analyze.
Blog posts might be a better form of writing than a book. Preparing and delivering a talk might be a better way to improve your communication (and "brand," for that matter).
However, if after thinking it through you still have an itch to write a book, it could be that you simply can't not write a book. In which case, go for it and do it well, and don't worry about justifying it.
It could be that the reason you should write is that you can't not write.
On the other hand: I'm a full-time author, but not because I feel any sort of compulsion to write. Writing books just happens to be one of the best ways to turn what I do feel compelled to do (reading/research) into something that benefits other people, and allows me to use what I'm good at doing in a way that supports my family.
Left to my own devices, I wouldn't write very much at all aside from note-taking. Turning random thoughts into readable long-form prose requires a ton of effort. It's worth it, but the work is difficult on the best of days.
I agree that blog posts, short essays, or private journaling are better tools for using writing for thinking. You don't have to worry so much about structure or the potential for misinterpretation, and most topics don't require hundreds of pages to explore.
For me, writing and programming feel very much of a piece. They seem to fire up the same parts of my brain, the feel like the same kind of mental exercise, and a completed project in writing or programming gives me the same kind of satisfaction.
Writing is an incredibly important communication skill, and it is a forcing function for understanding a topic. But still, writing a book is rarely the best use of your time nor the best way to learn to communicate or analyze.
Blog posts might be a better form of writing than a book. Preparing and delivering a talk might be a better way to improve your communication (and "brand," for that matter).
However, if after thinking it through you still have an itch to write a book, it could be that you simply can't not write a book. In which case, go for it and do it well, and don't worry about justifying it.
It could be that the reason you should write is that you can't not write.