While this might not actually be the reasoning, an advantage may be that motion reinforces a mission. Despite working on a web startup I do not have any internet at home -- I use public WiFi. This forces me to use the internet to get stuff done. It keeps me from surfing endlessly -- the occupational disease of every hacker.

Likewise, perhaps it makes sense to use Cambridge for early stage hacking, and SV for finding investors and building a business.