Many developers don't spend time on hacker news or even any of the similar forums. To be stereotypical, HN readers seem more likely to be young, working for FAANG in Silicon Valley, and not a middle aged sharepoint integration developer living in the Midwest (although obviously they are also on this site).

I've had developers who treated it like a job, did it, went home, and weren't interested in the Mythical Man Month (but intuitively knew some of these principles).

Everyone experiences things daily without fully appreciating the patterns and insights that could be derived from it (would be exhausting if we did)

The book most definitely helps tech workers.