Functionally 0% of companies are working on things as important or impactful as the atom bomb, and I include FAANG et al in that. Maybe a small handful of AI companies will actually put out something that important? But even most of them won't.
The vast majority of companies are putting web forms over a database. Letting one or two people hold all the technical knowledge for something like that is borderline fiduciary negligence.
That isn't the point; It's not about the importance
It's about specialized knowledge. To the owners of the business, making sure the business doesn't fail to deliver is existentially important.
Web developers are fungible. The guy who designed the carefully tuned graph database that runs on a custom Linux kernel with a custom tuned filesystem is not. If this sort of thing is critical to your business succeeding, that engineer might as well be Niels Bohr.
The vast majority of companies are putting web forms over a database. Letting one or two people hold all the technical knowledge for something like that is borderline fiduciary negligence.