How Expertise Makes Your Work Less Interchangeable

The idea is that in a professional service context, both parties need some control. So unless you specialize, you're not going to have the opportunity to do very good pattern matching. If this client who didn't hire the expert can find what they deem to be many suitable substitutes, then the expert had no power in that relationship. The only control an expert has in a professional services situation is to withhold their expertise.