Because they are not perfect and act like humans.
The diplomatic neutrality of the United States was tested during the Napoleonic Wars (1803-1815). The warring nations of Britain and France both imposed trade restrictions in order to weaken each other's economies. These restrictions also disrupted American trade and threatened American neutrality. As time went on, British harassment of American ships increased. Controversial measures included British impressment of American men and seizure of American goods. After the Chesapeake Affair in June 1807, pitting the British warship Leopard against the American frigate Chesapeake, President Thomas Jefferson faced a decision regarding the situation at hand. Ultimately, he chose an economic option to assert American rights: The Embargo Act of 1807.
Be ready for an attack/ threatening power.
