Enterprises have infrastructure teams because they have applications that need to solve business logic that cannot be solved by static sites alone. Even the simplest businesses invest in data processing pipelines to extract value from their data. When the scale of data processing becomes very large, they need to rearchitect their systems in different ways to better handle that kind of traffic.

So it helps to have in house infrastructure teams that can somewhat consolidate and invest in long term planning and architecture for computer systems and services required by these enterprises.