It’s tough (speaking as a consultant at a smaller company). Large company procurement/legal basically limits the viable pool of competing consulting firms to those with sunk capital in their own big legal/procurement. And the big 4 management consulting firms have all perfected getting that large company’s client relationship and landing contract after contract.

It’s the same reason the same big 4-5 federal contractors win most of the work. The sunk cost in needed bureaucracy is large, it’s hard for a small player to compete.

The root issue is big co procurement has taken accountability away from the people who actually use and understand the services. So in my company’s case it’s common to start a relationship with a counterpart at a firm very willing to invest in our services. Sadly the procurement bureaucracy really gets in the way of progress making everything more expensive for both sides. If you’re Accenture and McKinsey you just (unethically in my opinion) sink the cost but then milk the relationship for all it’s worth.

It’s really dilution of blame. Actually doing anything in a corporation is hard, paying McKinsey to do what they do makes it easier, therefore there is value.