Question

Why are autobiograhies not reliable source of information? ​

Answer 1

An autobiography may be more accurate if the author is being completely truthful and objective. It will be less reliable if the motives for writing the book are financially driven or driven by other factors.  A biography can be more objective and accurate if the author, a) knows the subject well and b) gets input from many and varied sources (i.e. both enemies and friends)  It really is the quality of the source content and research that determines reliability