Most companies have a CEO, a small C-suite followed by increasing numbers of EVPs, SVPs, VPs and so on, each managing a number of people. These companies are triangular with a well-understood tiering of roles and responsibilities. These organisations tend to have a highly-centralised marketing function that is excellent at demonstrating the value of the company's products to it's customers.
However, nearly all Professional Services companies are partnerships with many owners and leaders. The triangle doesn't fit these firms; they are much squarer, with many leaders. In these firms, as Ali Bone points out below, the key client relationships are often held by an individual on a one-to-one, Expert-to-Expert basis.
The requirement of the marketing function in a square firm is to facilitate each of their many Partners to build their relationships with their individual, small number of key contacts. This is fundamentally different to the requirements of a triangular firm.
When assessing which marketing technology is likely to be a good fit for a firm, looking at the structure of a product and what it is trying to achieve is a sensible place to start, long before product features or price come into consideration.