We've learned a lot about Vesta already

Remember (I do) that the Dawn mission was once tentatively canceled before launch?  Glad that didn't happen.

NASA Dawn Mission Reveals Secrets of Large Asteroid

 "Data also confirm a distinct group of meteorites found on Earth did, as theorized, originate from Vesta. The signatures of pyroxene, an iron- and magnesium-rich mineral, in those meteorites match those of rocks on Vesta's surface. These objects account for about 6 percent of all meteorites seen falling on Earth. 

This makes the asteroid one of the largest single sources for Earth's meteorites. The finding also marks the first time a spacecraft has been able to visit the source of samples after they were identified on Earth."

And when it's done here, then it will head to Ceres.  And I want to know, why couldn't it go somewhere else after that?