They have their purposes. But I would consider it a bad writing habit if an essay is cluttered with unnecessary "a"s or "the"s. And what makes you so sure as where to add "a"s or "the"s, at the same time, unknowingly changing writer's intention to your understanding? You don't change The Great Gat*****y's "a" and "the", because you would automatically adjust your understanding to the writer's intention.
Charles Dickens loved commas, George Orwell avoided them. There is no one “correct” English, but there are styles, or “accents” in your understanding.
