Bank and financial markets supervisors have to make sense of the complex mesh of principal-agent relationships between lenders, borrowers and financial intermediaries, and to make these contracts incentive-compatible – this requires quite an amount of international organisation and contract theory!
Think of, say, the seminal work by Jean-Charles Rochet and Jean Tirole on credit card schemes as twosided markets, which we still use today to understand the fast-changing world of retail payments.