If he had left that out, his Bible would have been only a pamphlet.
The title-page reads as follows: THE BOOK OF MORMON: AN ACCOUNT WRITTEN BY THE HAND OF MORMON, UPON PLATES TAKEN FROM THE PLATES OF NEPHI.
Wherefore it is an abridgment of the record of the people of Nephi, and also of the Lamanites; written to the Lamanites, who are a remnant of the House of Israel; and also to Jew and Gentile; written by way of commandment, and also by the spirit of prophecy and of revelation.

Written and sealed up, and hid up unto the Lord, that they might not be destroyed; to come forth by the gift and power of God unto the interpretation thereof; sealed by the hand of Moroni, and hid up unto the Lord, to come forth in due time by the way of Gentile; the interpretation thereof by the gift of God.

An abridgment taken from the Book of Ether also; which is a record of the people of Jared; who were scattered at the time the Lord confounded the language of the people when they were building a tower to get to Heaven.
"Hid up" is good.

And so is "wherefore"-- though why "wherefore"?
Any other word would have answered as well--though--in truth it would not have sounded so Scriptural.
Next comes: THE TESTIMONY OF THREE WITNESSES.
Be it known unto all nations, kindreds, tongues, and people unto whom this work shall come, that we, through the grace of God the Father, and our Lord Jesus Christ, have seen the plates which contain this record, which is a record of the people of Nephi, and also of the Lamanites, their brethren, and also of the people of Jared, who came from the tower of which hath been spoken; and we also know that they have been translated by the gift and power of God, for His voice hath declared it unto us; wherefore we know of a surety that the work is true.

And we also testify that we have seen the engravings which are upon the plates; and they have been shown unto us by the power of God, and not of man.