Context is key. This statement is part of a larger argument Paul is making to the Corinthian church, which was experiencing divisions and factions. They were identifying themselves w/—Paul, Apollos, Cephas, or Christ—based on who baptized them His primary point is to refocus the church on the central message of the gospel of Christ. It serves to counter the divisions by reminding them that their unity should be in Christ not in the leaders who performed their baptisms.

To show us the importance of understanding what we are called to do. It takes humility to say, this is beyond me, I’ll allow others do it and concentrate on preaching the word.