Reg Braithwaite: "What I admire about professions like Engineering and Medicine. In short, their Code of Ethics. Try this: Employ an Engineer. Ask her to slap together a bridge. The answer will be no. You cannot badger her with talk of how you hold the Gold, therefore you make The Rules. You cannot cajole her with talk of how the department needs to make its numbers, and that means getting construction done by the end of the quarter.

Engineers have a certain line that they will not, cannot cross. Doctors work the same way."

As important as ethics, it's that they are licenced practitioners - the rule of law is on them in some cases - they can be sued for malpractice if ethics are not incentive enough.