The incentive structures around technical books are pretty weird.

Most major publishers pay quite small royalty rates, so even a popular tech book won't actually make the author much money. And the effort to write a good technical book is pretty huge. Also, the set of people who will actually finish writing a book is quite a bit smaller than the set of people who aspire to. (An editor at O'Reilly told me once that only about 1/3 of the authors they sign deals with actually end up finishing the book.)

So for a book to appear, you need to find someone who:

1. Knows this particular topic in depth.

2. Is interested in spending a lot of time writing a book about it.

3. For relatively little money in return.

4. And actually has the discipline to finish it.

Not a lot of people in that set. It's also particularly hard for technologies that are in flux since the quicker the book gets out of date, the less value there is in writing it.

Former O'Reilly editor here: story checks out. The 1/3 might be a bit low -- I had some surprises (one guy joined the Peace Corps and moved to South America, plus usual divorces and deaths and job changes) but it felt more like 80% completed. This might be the rosy glasses of memory, though.

There's also a weird difference in incentive between writing the first edition and working on updates: if the author was just after "I wrote a book!" then they already have that, and won't be so interested in updating.

If they were made famous and now have a lot of work as a result of the first book, they may not have time for it. It's quite the delicate dance to get someone else to update the book: without the update, sales will drop, but 1st edition authors feel weird giving a lot of their (not sizable) royalties to someone who didn't write most of the text.

That is fascinating. As someone who has writing a technical book as a life goal, I'd love to ask--do you have any insights you'd be willing to share regarding how to get started?

Pick a topic you know a lot about, or are willing to learn a lot about. Start writing.

Are you already blogging? If not, I would start doing that. Writing short form technical articles and sharing them is like bootcamp for longer form writing. You'll learn the mechanics of organizing thoughts into a linear narrative, the discipline to finish, and you'll get feedback from readers about what works and what doesn't.

I blogged for a few years (and wrote thousands and thousands of comments on Reddit, which was also helpful) before I wrote a book.

Alternative to (3) - Company that owns a language and is willing to pay decent money for someone qualified to write a book in order to increase popularity

Yeah, this is viable, but the cost is quite high if you're paying a skilled software engineer for their time. The company driving the language can probably spend that budget better elsewhere. (For example, on online documentation that is more easily incrementally maintained and grown.)