If you have a sizable iTunes library, or heaven forbid you have a decent camera, the drivespace gets exhausted pretty quickly on these little notebooks. ...iCloud isn't going to back up tens of gigs of your RAW or DNG files, just little jpgs, and odds are you're not going to score a connection to the net everywhere you go anyway to stream everything, since this is a Mobile Computer, and not a desktop, making it pretty crippled.
So yes, now we're driving not only the computer, but a second spinning HD unit over usb, burning up the battery that much faster. Many HD's won't even run when on battery power or attached to a hub, or even without their own power supply. HD's are that energy thirsty.
All this no ports wireless stuff looks slick in commercials, but the amount of drivespace & wifi bandwidth available in the machines hasn't increased proportionately to make it feasible yet.