Most of the big software companies have converged on the same model: many employees work on shared infrastructure that is not connected directly to any one product. Other employees use that infrastructure to build products. This means that employees working on products have great tools built especially for that company’s needs, which speeds up product development a lot. And the company can hire highly skilled, highly specialized and highly paid engineers to build the infrastructure.
I’ve considered only software companies in this article because they are what I know best.