Every visible assembly of believers, since the resurrection of Christ, has formed leadership and authority within their members, due to the teachings of Holy Scripture.
This developed into two major camps: The Presbyters and the Congregationalists.
The former, designating and anointing Elders, who subsequently choose other Elders; all answerable to their system of Presbyter Sessions.
The latter chose to designate Elders according to local and independent congregational votes and majority; answerable only amongst themselves.
Either way, Protestant churches, if they are scriptural, name Elders for their own oversight and authoritative rule as taught by Paul.
To suggest the bible does not say enough about these matters, is simply an unrealistic denial of church history and very unwise, for:
No Eldership or no formal authority in an assembly of worshipers, will denigrate into lawlessness.
Unscriptural abuse and too much (human) authority given to Eldership in an assembly, can lead to magisterial politics (e.g. the Papistry).