There's some reason to think that the core is unsuitable for other reasons. There are a few lines of evidence (see link below for one I could find fast) that the core of our galaxy undergoes periodic starbursts every few hundred megayears in which it has a brief episode of very concentrated rapid star formation, followed by a period of a few tens of megayears in which the supernova rate in the core temporarily exceeds the steady state galactic supernova rate by a factor of 50+. The high rate and small volume (less than 1/500 the galactic volume) would lead to quite the occasional local sterilization event if this does indeed happen on a regular basis.

http://www.nasa.gov/mission_pages/GLAST/news/new-structure.html