Jesus said to them again, "Peace be with you. As the Father has sent me, even so I send you."
The Catechism tells us that Mass is called Mass "because the liturgy in which the mystery of salvation is accomplished concludes with the sending forth (missio) of the faithful, so that they may fulfill God's will in their daily lives." In other words, for the vast majority of us, the work of the Gospel is to be done in the world, not in the sanctuary. At the altar, the priest presides because it is his task to hand on the Tradition and the sacraments to us. But in the world, we laypeople preside because it is our task to teach, sanctify and govern the world with the authority of Christ. In short, we laypeople have an office and we are sent to fulfill that office by the same Spirit of Christ Who sent the Apostles. We are not just schlepping out the door to kill time till it's time to go to Mass again. We are sent. God's word to us at the end of every Mass is "Go! You are sent!"