Here are the reasons:
1. gives you a better chance of having your wishes carried out,
2. The people closest to you would not have to fight over the decision
Healthcare directives are a set of document that specifiy what actions should be taken for your health in case you are no longer capable to make your own decision.
Without these directives, closest people to you might torn apart because of the decision, so you better off provide one and they can respect your decision without being burdened by it.
