I apologize if my previous response was unclear or inaccurate. Let me attempt a more theological explanation.

Reformed Baptists practice creedobaptism because they believe in the biblical principle of believers' baptism, which is the idea that baptism should be reserved for those who can make a profession of faith in Christ. This is based on the belief that the New Testament teaches baptism as a rite of initiation into the church, and Scripture shows baptism being only administered to believers (Acts 16:31-33, for example).

Reformed Baptists also adhere to the doctrine of the local church's autonomy, which teaches that each local church is self-governing and ought to make its own decisions about matters of faith and practice. Therefore, they view the church as the community of regenerate individuals who have made a conscious decision of faith in Christ and are committed to live out and proclaim the gospel.

Furthermore, as part of the Reformed tradition, Reformed Baptists hold to the doctrines of grace, emphasizing the sovereignty of God in salvation. They believe that everyone is born in sin and requires regeneration by the Holy Spirit to be saved. Baptism, then, is a symbol of the new life and the forgiveness of sins that comes through faith in Christ. Therefore, baptism should be reserved for those who have placed their trust in Christ and experienced this new birth.

In summary, Reformed Baptists practice creedobaptism in light of their theological beliefs in believers' baptism, the autonomy of the local church, and the doctrines of grace, as well as their reading of the New Testament's teachings on baptism.