The purpose of these kinds of documents is to allow you to share your preferences about medical treatment in extreme situations where you are unable to communicate. One such example is if you become incapacitated at the end of life, and your health directive can stipulate your preferences about what you wish to happen at the state and time. Putting these preferences in a clear legal document ensures that your preferences are known by others in the event that something happens to you.
This can cut out the problems of a physician having to obtain a consensus about your next steps in medical treatment from your family members. Not every family member may agree with your wishes, but you will want to eliminate the possibility of circumstances were family members are arguing with one another about how you should be cared for. Designating a healthcare proxy in your health directive can specify the individual whose direction is to be followed in such situations. If you want to prevent your family members from having to make hard decisions on issues about which they may not agree, outline your wishes in a healthcare directive.