In many churches, size will prevent each member from getting to know every single new person who ever comes to a meeting of the church.
Yet a church needs to assess the credibility of someone’s profession of faith in Christ (Matt. 18:18).
The elders are entrusted with the oversight of the church (1 Pet. 5:2). They are appointed to the office of elder precisely so that they can keep a close watch over the whole flock (Acts 20:28).
So, even though it is ultimately the church’s responsibility to evaluate, affirm, and oversee a member’s profession of faith, it is a good idea for each prospective member to be interviewed by one of the church’s elders.