The big employers, for better or worse, in may cases still favor their mothership. Give the choice they seem to favor the HQ if they can. The satellite offices are required for scalability, but as long as they have capacity in the main office, they'll try and fill those slots up first.
Oh. I don't disagree. I think it's hard to give up the mothership vs. satellite mentality. I work for a company that had two major locations fairly early on (not including SV) for historical reasons and that's doubtless one of the factors that's made it easier to be pretty distributed as time's gone on.
At least its how it feels like.