There's a simple explanation for that, Chef, as I tell my literature students: history is what we've got, and fiction is what we want. Given that choice, which would you choose? As T.S. Eliot says, history is the experience, myth is the meaning.

But if what you're really objecting to is fiction presenting itself as history, I agree with you there. That's a tad irresponsible of Hollywood to do that as it often does.