If history is the teacher of life, why do we still have wars, oppression, dictatorships, etc.?
Either we don't want to learn from history or history is subject to fabrications and lies. Mankind cannot learn from fabricated and non-truthful stories and sources.
Napoleon said once:
“To write history one must be more than a man, since the author who holds the pen of this great justiciary must be free from all preoccupation of interest or vanity.”
Truth is very important for progressive development of mankind and civilizations. Sources which allow lying and non-truthful acting like some religious sources (Ahadith, Talmud...) create states of oppression, injustice and wars. That's why Quran stresses the struggle for truth and evidence.