The last will normally contain the name of an executor. If you don't have any executor than the court name taken in the will. In some state incase person die with proper last will than the proceeding not needed by court. Many states in US needs proceedings are execute in the court.
In case death of person, the property will automatically transfer to spouse, kids and descendants. In case person die with no legal provision of their property than the Intestacy law appoint representative to perform the legal proceedings.
It is essential to prepare a last will to avoid proceeding, because it takes lot of time for the proceedings. If person die without will than it must be clear that who will be ultimate owner of the property after the death of testator. In this case it is better to establish trust to transfers ownership.
The last will ensure family member to get the assets or other belonging in case person die. If you do not have any successor and you will die without last will than your state may claim your property.