Because "Attack of the 15.24-Meter Whatever" just doesn't have the same ring to it. This is like Incredible Shrinking Man, except that the ray gun that zapped the character was set on "Grow" instead of "Shrink". Now the protagonists have a huge problem to deal with. This generally violates the Square-Cube Law, but that's okay. For humans, expect Magic Pants to be in effect -- can't have a giant *naked* person, after all. The Moral Guardians would freak. See also: