Faustus hands over his soul for the ability to perform magic. Although he imagines using magic to make himself as powerful as a god and as wealthy as a king, when it comes right down to it Faustus's magic often amounts to little more than fancy tricks. He uses it to make the images of dead people appear in order to amuse himself and his friends, or to humiliate people, including peasants who have done nothing to harm him. And the townsfolk who use magic do silly things like steal dishes and bogart some booze. In the end, magic in Doctor Faustus, however incredible, appears to be no more useful than the man who wields it.
Magic is might. Faustus wants magical powers so he can control others—nothing more.
Faustus's magic isn't all that awesome in the first place. Parlor tricks don't change the world.