The work of the Great Commission begins with telling about Christ, but then it continues with discipling those who are ready to hear the message. We must be willing to come alongside others and help them. Baptism is a result of a commitment to Christ. Being nice to people and helping them is important. But at some point we must be willing to ask them if they want to make a commitment to Christ.
Baptism is the public confession of the commitment they have already made in their heart.
But if we never ask people to make a commitment, people will not be able to experience spiritual growth which can only come from a transformed heart. Once a person has made a commitment to Christ and been obedient in baptism, they must be instructed in the ways of God. Without proper teaching, followers of Christ will be stunted in their spiritual walk. New believers will be taught as they read the Bible, they will be taught by the Holy Spirit, and they will be taught as they spend time in prayer with God. But God also wants us who are established Christians to invest time and effort in sharing what we have learned.