It seems like a requirement to clear whole areas unless you jump around to every zone at or below your level (and sometimes complete an area and jump to lower level zones) to keep up with the min level requirements for your story. Good re-playability so far, I'm not much of a PVP person, but I'll try it at some point.
And hey, SWTOR was amazing... until you hit the end. Speaking of, I heard Star Wars is going to be free-to-play very soon.