JOEL - Because Jesus can also be called "Everlasting Father" or "Eternal Father".
King Benjamin said that for those who enter a covenant with Jesus,
"he hath spiritually begotten you; for ye say that your hearts are changed through faith on his name, therefore ye are born of him and have become his sons and daughters." (Mosiah 5: 7)
Christ is an "Everlasting Father" for those who become His sons and daughters through covenant and obedience to His commandments.
In the Book of Mormon Abinadi said:

"Teach them that redemption cometh through Christ the Lord, who is the very Eternal Father." (Mosiah 16:15)

Jesus can be referred to as "Father" in the following three ways:
1. He is the Father of those who accept the gospel because it is through his atonement that the gospel is made active on the earth, as I explained above.
2. He is the Father of this earth in the sense that He created this earth under the direction of his Father.
3. He is the Father because of divine investure of authority, meaning that Jesus has been given the power to act for and represent his Father on this earth.