Tim Williams on the Ignitions Consulting Group blog writes:
The agency business is severely limited by its inability to scale. […]
The problem with the agency revenue model is that agencies don’t actually have a revenue model; they only have a cost structure. A revenue model is a framework that identifies how an organization generates income, including specific offerings, pricing approaches, value classes, customer segmentation, pricing tiers, and more. An effective revenue model produces multiple revenue streams based on innovative pricing strategies. The billable hour hardly meets that definition.
If the agency model is this constrained, imagine how bad it is for solo professional services providers.