Why is Growth in Godliness Important?

Nurturing growth in godliness is the primary obligation of the church.

And He gave some as apostles, and some as prophets, and some as evangelists, and some as pastors and teachers, for the equipping of the saints for the work of service, to the building up of the body of Christ; until we all attain to the unity of the faith, and of the knowledge of the Son of God, to a mature man, to the measure of the stature which belongs to the fullness of Christ. As a result, we are no longer to be children, tossed here and there by waves and carried about by every wind of doctrine, by the trickery of men, by craftiness in deceitful scheming, but speaking the truth in love, we are to grow up in all aspects into Him who is the head, even Christ, from whom the whole body, being fitted and held together by what every joint supplies, according to the proper working of each individual part, causes the growth of the body for the building up of itself in love (Eph 4:11-16).

The church is the primary context for equipping (vv11-13).

Equipment for ministry does not happen primarily at the seminary, or in the parachurch, or even in a mission agency. Each of these resources has its own rightful place in the training of ministers and missionaries, and we should praise God for the help they provide. But their rightful place is a secondary one.
According to Ephesians 4, equipment for ministry primarily happens in the context of the local church, under the mentoring leadership and discipling influence of God-gifted pastors and leaders.
Because this is true, it is incumbent upon pastors to be looking constantly to build into younger men who have leadership potential.
This way, if they do go to seminary, they will already have been trained by the local church for the practical side of the ministry, and they will have already been taught how to put their seminary training to work in the context of a local church.