Here's why:
* The film covers a broader scope: "The Patriot" tells the story of Benjamin Martin, a fictional character, and his family's struggle during the American Revolutionary War. The film spans several years and various battles, including the Battle of Cowpens and the Siege of Charleston.
* Yorktown serves as the climax: The Battle of Yorktown, while significant, is essentially the final act of the movie. It's the culmination of the protagonist's journey and the turning point in the war.
So, while the Battle of Yorktown is a key event in "The Patriot," it's not the sole focus of the narrative. The film explores broader themes of family, sacrifice, and the human cost of war through the lens of Benjamin Martin's story.