You pretty much answered your own question. Paul, the apostles, are successors to Christ. They can plant and water the seeds, but the holy spirit, through their words, makes those seeds grow within you. Remember that Paul and the apostles were given autoritity to spread the seeds to the whole world. You see, I believe that God is a God of order. Not disorder. Would you leave your instructions with plp you didnt first train.
Below are just a few of the passages, that show how the apostles were given authority over the flock of Jesus.
Matt. 10:1,40 - Jesus declares to His apostles, “he who receives you, receives Me, and he who rejects you, rejects Me and the One who sent Me.” Jesus freely gives His authority to the apostles in order for them to effectively convert the world.
Matt. 16:19; 18:18 - the apostles are given Christ’s authority to make visible decisions on earth that will be ratified in heaven. God raises up humanity in Christ by exalting his chosen leaders and endowing them with the authority and grace they need to bring about the conversion of all. Without a central authority in the Church, there would be chaos (as there is in Protestantism).
John 13:20 - Jesus says, “he who receives anyone who I send, receives Me.” He who receives the apostles, receives Christ Himself. He who rejects the apostles and their successors, rejects Christ
Acts 20:28 - the apostles are shepherds and guardians appointed by the Holy Spirit / 1 Peter 2:25 - Jesus is the Shepherd and Guardian. The apostles, by the power of the Spirit, share Christ’s ministry and authority.
Eph. 2:20 - the Christian faith is built upon the foundation of the apostles. The word “foundation” proves that it does not die with apostles, but carries on through succession.
Acts 1:15-26 - the first thing Peter does after Jesus ascends into heaven is implement apostolic succession. Matthias is ordained with full apostolic authority. Only the Catholic Church can demonstrate an unbroken apostolic lineage to the apostles in union with Peter through the sacrament of ordination and thereby claim to teach with Christ’s own authority.
Acts 1:20 - a successor of Judas is chosen. The authority of his office (his “bishopric”) is respected notwithstanding his egregious sin. The necessity to have apostolic succession in order for the Church to survive was understood by all. God never said, “I’ll give you leaders with authority for about 400 years, but after the Bible is compiled, you are all on your own.”
The collective wisdom of apostolic succession has governed the Catholic church through 2000 yrs.
This link should provide many passages from the bible that support the importance of Apostolic succession and its importance
scripturecatholic.com/apostolic_succession.html