* As President of the Continental Congress: Hancock was the presiding officer of the Congress when the Declaration was adopted. It was standard practice for the presiding officer to sign official documents, and this made Hancock's signature the most prominent one on the document.
* Symbol of Rebellion: Hancock was a wealthy merchant and prominent figure in Boston, making him a target of British authorities. His bold signature, large and clear, served as a defiant declaration of independence. It was a way of saying, "Here I am, come and get me!"
* Publicity and Legitimacy: The Declaration was meant to be widely circulated and read, and Hancock's signature, both by its size and his notoriety, would have helped ensure the document received the maximum attention. It also added a sense of legitimacy and authority to the document.
Essentially, Hancock's signature was both a practical necessity and a powerful statement of defiance and commitment to the cause of independence. It became a symbol of the American Revolution, a reminder of the risks taken by those who dared to break free from British rule.