This is it right here. A shocking percentage of corporate boardrooms are McKinsey alumni — by hiring McKinsey to develop or even just validate your strategy, you buy credibility from the people who sign the checks because they know and trust senior people at McKinsey.

Consulting is a relationship business. The other purpose of consulting at the boardroom level is to enable companies to sidestep laws around collusion and insider trading — the SEC occasionally charges somebody, but it’s largely symbolic given how pervasive it is. It’s not unheard of for CEOs of companies that are direct competitors to have regular calls to discuss strategy, all while using consultants to create a paper trail that says the strategy was developed through rigorous analysis.