JOEL - The History of the Church was mostly written(or directed to be written) by Joseph Smith, but it was never considered scripture; it was mostly just history. However, many of the sections of the Doctrine and Covenants are found in that history.
Because of his lack of formal education, Joseph Smith depended on others to do most of the actual writing. Many other scribes, clerks, and historians were involved in that work; especially Willard Richards, Joseph's private secretary and church historian, who also wrote the section about Joseph's death. In contrast, that which was considered scripture, such as the Doctrine and Covenants, was written down exactly as dictated by Joseph Smith.
I am not sure why you think that everything that Joseph Smith wrote should be considered scripture. For example there were other writings and several personal letters he wrote to his wife Emma and other people which would obviously not be considered scripture, even though he may have spoken about Church doctrine in them. I am sure there were many things that Moses or Isaiah or John the Revelator wrote that are not included in the Bible.
In our day there is a process that is followed for anything to be considered scripture and be included in our canon. None of the past prophets of our Church were perfect or infallible, therefore, to be certain any potential scripture truly comes from God, it must first be presented to the other Apostles of the Church for their agreement and support, and then, in accord with the law of common consent, be accepted by all other members of the Church.