A graduating structural engineer has no idea how to marshal a design through the building inspector's approval process. A graduating lawyer has no idea how to actually engage in litigation.
The point of his post is that the market opportunity doesn't exist because the firms professionals are expected to enter take care of that domain-specific training themselves.
For a very long time there has been a "tradition" of sending newly graduated engineers to work on the manufacturing floor, or in product testing for a while so they get background in the business before actually having to design anything. Such a tradition seems to be missing in software development.
Why not, looks like a gap in the market.