Exodus 20:8 is the fourth Commandment, "Remember the Sabbath day by keeping it holy." In a modern society people do not even recognize it as important. Most businesses are open on Sunday's, and many people work on Sunday.
Just because a job requires one to work on Sunday does not give an actual excuse to forget the Sabbath day. Nobody forces Sabbath to be celebrated on Sunday. The point of the matter is not worshiping on Sunday, the point is having one day per week to reflect on Christ.
Every human should have one day a week (at the very least) to focus intently on God's word and to reflect on their previous week to see how they could have reacted to things, or what they should be doing different. In this time, prayer is important. The reason why one should take a full day is so they are not preoccupied with work, life, etc.
One day per week is critical to pray for the weeks ahead, to pray for forgiveness to the way they were previously, and to reflect on Christ's love for us. Diving into God's word keeps us focused on what is important, and allows us to receive the knowledge to live Godly lives.
Remember, our goal as Christians is to be as close to God as humanly possible. We are supposed to be fit to speak of God, to teach about God, and to set the example of being like God. If one does not know God's work, word, and love, how are they to live a Christian life?
By remembering the Sabbath day, one is able to improve and understand their personal relationship with Christ. If Christ doesn't know you when the time comes, Hell will. Unfortunately many people don't seem to understand the importance; it doesn't take kindness and love, it takes Jesus and understanding. The fourth Commandment is indeed important, it is a key to your salvation.