WHY JUST BORN AGAIN?

Jesus says that if one desires to be his disciple, he must deny himself, pick up his cross, and follow Him. 

He says that whoever seeks to save his own life will lose it and whoever loses his life for His sake will find it.

Then the Apostle Paul tells the Galatians that he himself is crucified with Christ and the life he now lives in the flesh he lives by faith in the Son of God.

And to the Philippians Paul describes his desire to know Christ and the power of His resurrection and the fellowship of His sufferings - being conformed to Jesus in His death - and by doing so, attain to the resurrection from the dead.

Paul tells the Romans that if they are united with Christ in His death, they will surely experience a resurrection like His as well. 

So how is it that "you must be born again" becomes the predominate and exclusive descriptor of the Christian experience? 

Why do we speak metaphorically of "born again Christians" but never "crucified Christians"?