For the simple reason that just as you are doubting various books of the Bible, in the 1500s the various reformations (first, second, third etc) led to wholescale doubts of the entire canon by various groups including unitarians, etc.
But that was for Protestants -- for varying groups, Christian and non-Christian such as yours, Seventh Day Adventists, Mormons, etc. that's now your prerogative to toss out as many books as you want to
For the simple reason that just as you are doubting various books of the Bible, in the 1500s the various reformations (first, second, third etc) led to wholescale doubts of the entire canon by various groups including unitarians, etc.
But that was for Protestants -- for varying groups, Christian and non-Christian such as yours, Seventh Day Adventists, Mormons, etc. that's now your prerogative to toss out as many books as you want to