If teleportation did exist, teleporting relative to Earth sounds like pseudo-sciencey wishful thinking.  However, teleportation relative to a gravity field could accomplish the same thing and much more plausible.  Likewise with time travel— if you're not time traveling to the same point in space years earlier or later, but traveling to the same gravity-spacetime point, that makes the whole concept more digestible, even if it's all just a science fiction plot device.