Because the scripture does not teach that.
Ephesians 2:8
For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast.
1 Peter 1:5Who are kept by the power of God through faith unto salvation ready to be revealed in the last time...9Receiving the end of your faith, even the salvation of your souls.
1 John 5:4For whatsoever is born of God overcometh the world: and this is the victory that overcometh the world, even our faith.