Mosiah 21:35

"They were desirous to be baptized as a witness and a testimony that they were willing to serve God with all their hearts..."

The people of Limhi repented of their iniquities and wanted to be baptized because they love the Lord.  They  realized the joy and protection that comes from serving God. Baptism is a covenant made with God to serve him and is also a way to receive so many blessings.