Why don't textbook address the shortcomings of historical figures?

History is made by those who see a man/woman as interesting/worthy to be written about...and only those stories that are either heroic or atrocious are deemed interesting enough to keep them going on throughout the ages. We know plenty about the impotence of King Richard VIII. History likes to show the shortcomings of historical figures who are viewed as evil.

Historical figures make up the cornerstone of American ideology and policy. They are all wrapped up with American sense of patriotism and fervour. Bad guy and good guys must be clearly defined and this must never change.