Jesus performed many miracles that are not recorded in detail so when detail is provided it is because it shows us something important about the Lord.  In turning water into wine Jesus provided evidence that he was the creator God, able to make something from nothing.  The parallels between Jesus' temptation in the wilderness and this miracle point to the importance of using God's gifts to bless others and not for ourselves.  In creating around 150 gallons of good wine, Jesus showed that God is not afraid to give good gifts even when they have potential for abuse.