You need a Will if you want someone you know and trust to administer your estate.
That’s a lot of responsibility and authority. Although the Administrator does not get to decide who receives assets or how much each person gets, they do get to make most other decisions, including how long the process takes and (sometimes) who might receive a particular item.*
While there is not a law that says who the Administrator must be, there is a law about who it can be, along with a prioritized list,** in case the Court has to choose between people who are fighting about who gets to do the job. (This happens more often than you might think.)
That list includes creditors. So anyone you owe money to when you die can ask the Court to be named as the Administrator of your estate. This list also allows almost any mentally competent adult, regardless of their relationship to you or your family.***
However, in a Will, you get to pick who administers your estate. This person is called an Executor, and they have the same job as an Administrator (collect & preserve, pay, and distribute).
In your Will, you can choose someone you trust to carry out your wishes according to your Will. And you can choose alternates, in case your first choice can’t or won’t do the job.
(And, if you are worried that naming a particular family member might cause hurt feelings or conflict in your family, you can choose a neutral professional—such as a CPA, financial planner, etc.,—to serve as Executor, instead.)
*So long as the item is not given to a particular person in a Will, and other conditions are met.
**See O.C.G.A. § 53-6-20
***See O.C.G.A. §§ 53-6-1 and § 7-1-242