Actually think about it. When you use the time machine, you probably wont move right? If you go back or forward even a small amount (say a day or more), odds are you will end up somewhere in space. If you go a year or more, you will probably end up way out in deep space, if you calculate in the motion of the solar system as a whole (orbiting around the galactic core).
TL;DR : people who use time machine need to fly their asses back to earth, thus wtf is the point.