I disagree. Historians are constantly making predictions of events happening today, based on their knowledge of history. Some are accurate, some are not. They can then take this output, and use it to refine the views of history.
This doesn't even cover how history is written by very unreliable narrators, and historians have to do more than learn the "what" to uncover the "how".
Your argument is also somewhat limited to History, when Philosophy, Psycology, and other liberal arts degrees do not have the same limitations.