Why Justifcation by Faith ?
Those who are Justified before Faith before God, based upon The Divine Purpose which includes the blood of Christ in covenant, slain from the foundation Rev 13:8, foreknown before the world began 1 Pet 1:20, based on the blood of the everlasting covenant Heb 13:20. They all shall be Justified by Faith in time at their call by the Gospel Rom 8:28-30
28 And we know that all things work together for good to them that love God, to them who are the called according to his purpose.
29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.
30 Moreover whom he did predestinate, them he also called: and whom he called, them he also justified: and whom he justified, them he also glorified.
Its at this Call they do receive a sense and knowledge of it [Justification], they now know themselves Justified in their consciousness to be Justified before God through Spirit wrought Faith 1 Cor 6:11
11 And such were some of you: but ye are washed, but ye are sanctified, but ye are justified in the name of the Lord Jesus, and by the Spirit of our God.
For Faith is a fruit of the Spirit Gal 5:22, and men do not have it [Justifying Faith] by Nature; and men by nature [even the elect] have no way of knowing of such a spiritual blessing as Justification before God until they capacitated by the fruit of Faith from the Spirit, and only to those is the Gospel sent to reveal this Justification / Righteousness to Rom 1:16-17
16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
17 For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
This Righteousness revealed to Faith is the basis of their Justification before God.
So its only proper in the arrangement of Salvation in the Dine Purpose, that those Justified before Faith, are Justified by Faith or through Faith knowingly and consciously. For what comfort or peace can come from it [Justification before God] if its never made known to the one who is. For Justification by Faith is the beginning of the assurance of Faith Heb 10:22
22 Let us draw near with a true heart in full assurance of faith, having our hearts sprinkled from an evil conscience, and our bodies washed with pure water.
Without Justification by Faith there would be no Joy and Peace in Believing Rom 15:13
Now the God of hope fill you with all joy and peace in believing, that ye may abound in hope, through the power of the Holy Ghost. 7