Well considering that his Star Trek movie ripped off... sorry, paid homage, to the Star Wars films a lot... It's no wonder Abrams declined. He's already directing a Star Wars movie.

Of course, it also means we've missed the chance of Episode VII taking place in some uncharted planet somewhere with Luke/Leia/Han or their expies journeying through Inter-Galactic Purgatory while trying to figure out the significance of the number 47 to the Force.