Tree structured hierarchies are studied in the field of computer science. A rooted tree makes one node the root node.
A general relation between any two elements can induce a tree or tree-like structure. The relation "is the parent of" induces a tree-like structure called a DAG (Directed Acyclic Graph). Thus, a family tree is not actually a tree but a DAG. The undirected form has cycles. Why?
In computational terms (of computer science), a tree structure representation, in contrast to a flat linear structure representation, results in order log(n) performance rather than order n. This can result in significant performance increase as n get larger.

In human systems, however, the tree structure may be used by the humans to get some advantage, or be "greater" in some respect, over other members in the tree.

More: Graphs and graph theory

The relation "is greater than" when applied to pairs of people induces a tree-structured hierarchy.

The relation "serve tables" when applied to everyone creates a tree-structured hierarchy. The word translated as "reason" is that of "best" as in "greater" or, by implication, "lesser".
Out of this simple start, a huge and complex church hierarchy developed. In the fourth century, it grew from a collection of seeds into a huge tree such that the birds of the air come and made a home in the tree.

More: Matthew 13:31-32 Third kingdom parable: mustard seeds and trees

More: Exodus 18: Hierarchy as a man-made tree structure

The ancient Greek word "ἄριστος" ≈ "best" as in the "best" warrior. That is, the "twelve" considered themselves the "best" as in "greatest" and therefore did not "desire" to "serve" "tables".

☐ Was it the "best" solution?
☐ Was it the most "desirable" solution?
☐ Was it a "reason"?

Discuss: How might this decision have impacted a sense of "greater" or "greatest" and, by implication, have started the move to a hierarchical church structure?

The Latin word "aequus" ≈ "equal, level, fair, just" which starts the word slide found in most modern translations.

NIV (New International Version): So the Twelve gathered all the disciples together and said, “It would not be right for us to neglect the ministry of the word of God in order to wait on tables.

NLT (New Living Translation): So the Twelve called a meeting of all the believers. They said, “We apostles should spend our time teaching the word of God, not running a food program.

Berean Literal Bible: So the Twelve, having called near the multitude of the disciples, said, "It is not desirable for us, having neglected the word of God, to attend tables."

The ancient Greek word "ἄριστος" ≈ "best" as in the "best" warrior which requires an "opinion" on which of two are the "greatest" according to some "best" criteria.

To support the idea of "pleasing" or "desirable", Strongs relates the word for "best" to the ancient Greek word "ἀρεσκω" ≈ "pleasing". I could not find a direct connection in any etymological reference or lexicon.