When it comes to the Great Commission, God could have also said "Stay and Radiate". He could have only required that we live a "good" Christian life and as people viewed us they would be convicted of their need for Jesus.
But, God did not command that - He said "Go", we are to be intentional about going to the lost world (not just hoping they come to us). And He said "Preach", speak verbally the Gospel to those we go to (not just hoping they will believe through "lifestyle evangelism")
And he said unto them, Go ye into all the world, and preach the gospel to every creature.