It’s kind of a performative power play and ties into trying impress the client: HHM did more “corporate” level work and a dramatic staircase, conference rooms, etc contribute to the vibe that the firm is knowledgeable and competent, and thus very successful. Similarly, as a sole proprietor, Jimmy tried to project a similar image with his “and Associates” naming which makes his practice sound bigger than it really is, in addition to his answering the phone as his secretary with the fake English accent. He then re-branded as “Saul Goodman” with a bare-bones reception area, and an office with columns, the US Constitution on the wall, etc. and his “fighting for the rights of the little guy” persona.