Why do academic writing standards condemn pronouns like I, me, my, you, and your?

Why are pronouns like I, me,my, you, and your used in the first and second person condemned in academic writing standards?

There is a distinction between formal and informal writing. Personal pronouns are considered informal as you would write a letter to a friend. Academic writing is supposed to be formal. It's like holding your pinkie finger up when you drink a cup of tea. Nobody has any idea what the purpose is but that's how it's "supposed to be" done.

The choice of words that gives the reader a clear mental picture makes the best communication. However, if the purpose of the writing is to get the best grade, "supposed to be" always wins.