Since no one in this life can obey the Ten Commandments perfectly, why does God want them preached so pointedly?

First, so that the longer we live the more we may come to know our sinfulness and the more eagerly look to Christ for forgiveness of sins and righteousness. Second, so that we may never stop striving, and never stop praying to God for the grace of the Holy Spirit, to be renewed more and more after God’s image, until after this life we reach our goal: perfection.