Because Jesus, the Son of God, is the Father's only provision for redemption. He, Jesus, is the only way, only truth, and only source of life.
Without Him there is no salvation.
John 17:3 And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.
Joh 14:6 Jesus saith unto him, I am the way, the truth, and the life: no man cometh unto the Father, but by me.
Acts 4:12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.