A small list, a senior audience, and very little room for noise
Professional services marketing does not work like volume marketing and firms that try to run it that way damage the thing they depend on. The audience is a few thousand people, many of whom could commission significant work, and their attention is the scarcest resource the firm has access to. Every send spends some of it. The routine therefore optimises for being worth reading rather than for being frequent.
This is why the automation in a professional firm looks so different. It is not a series of drip sequences designed to warm somebody up. It is a mechanism for making sure the insight mailing actually goes out, that everyone who attended a webinar gets a proper follow-up, and that the client from two years ago is contacted by the partner who knows them before a competitor gets there.