If "All scripture is inspired by God", then they are just as valid.<quoted text>
How come the church of Christ doesn't have the gospel of Thomas or gospel of Mary Magdalin in their canon? They both were Apostles of Jesus Christ. There is definitely evidence of some Christian sects (gnostics) using those books very early on.
Unfortunately, MEN DECIDED that they could play "God" and choose what you are to believe or not.
One does not need a specific religion to understand this.