The reason why so many officials and their supporters focus on Ground Zero is to maintain psychological — and thus voting and working — support for the Empire, its soldiers, its taxes, its outposts, and its wars. It also builds and maintains support for the growing police state at home.
The State makes itself out to be the only supplier of national security. Anything that advertises its supposedly unique role helps it sell its product and gain support for that product. Ground Zero is an advertisement that "you need us (the State) to protect you". The fact that the protection is so bad that 9/11 happened in the first place, and that the protectors elicited the terror directed against Americans, is ignored. Those who insist on maintaining this land as a never-to-be-forgotten symbol, or on making martyrs out of those who died, are supporting this advertisement for Empire abroad and repression at home.