Mine was ordered for my wife so its not linked to my account, and I still haven't received a shipping notice.
I suspect its a geographical limitation, they're probably shipping stuff from hubs. If you're close to a hub you'll get it sooner.
I'm guessing, but I imagine large organizations like Google have deals with the carriers so that they don't flood the system with mass shipments. For example say they have a huge warehouse in the Chicago area with a bunch of stock, if you live in Chicago you'll get it put straight into the carriers system and you get it the next day, if you live in WA, they collect the days worth of orders going to WA (say 10,000 orders) box it up in one container and ship it to Seattle. Then it enters the UPS system at a different point in the system, closer to its destination, but a couple of days after it really started moving towards the customer.