Because the American citizenry has relatively little power over the actions of government in general. Thanks to a system of representative democracy, Americans

Because the American citizenry has relatively little power over the actions of government in general. Thanks to a system of representative democracy, Americans can only really choose from a limited pool of politicians to influence the law-making process -- and there aren't any major politicians there which want to change copyright law (that I know of!). The main alternative to engaging in electoral politics are protests, demonstrations, general strikes, etc.