[jcrawfordor]

The data isn't location based, it's the same for everyone. The GPS control center updates it once an hour or so, but it's applicable globally. As the article explains, GPS satellites broadcast it, but at a low bitrate so it takes a long time to receive. Much faster to just download it from the internet. Because of the architecture of GPS in phones (which is basically a historic artifact, the chipset is expected to provide NMEA sentences and the OS doesn't want to be more deeply involved than that) AGPS needs to happen at a fairly low level.