so they can have boundaries and so we can have rights
Cabinet members in the United States must go though senate confirmation and be approved by the senate before they can be appointed to their position.
The appointee must have a background that is compatible with the department he/she will head. The appointee must have skills and experience.
This is an example of the Pygmalion effect.
The Pygmalion effect or commonly known as the Rosenthal Effect is credited to Rosenthal and Jacobsen.
This Pygmalion effect is a type of self-fulfilling prophecy wherein you think something will happen and you may consciously make it happen.