Mark’s target audience is Gentiles (non-Jews). He leaves out details that would only have been of interest to Jews and occasionally explains things only a Jew would have known. In our chapter today, Mark is showing, in a summary way, how Jesus was prepared for his ministry.
If part of the preparation for ministry for Jesus includes baptism, how much more important is it for us to be baptized? It’s how we declare to everyone we are following Jesus and is a key indicator we are going to do what God tells us moving forward. If you have trusted Jesus but have not been baptized, consider following Jesus’ example.