why does the xoom dock connect the USB port?

I feel like I must be missing something. I got the Xoom dock from Verizon along with my 4G upgrade (The turn around on the whole thing was 1.5 days, and the 4G is amazingly fast, so, definitely don't put that off if you have that option), and it powers the device AND plugs a USB connector into it (making it kind of tricky to seat correctly on the dock, since the connector is a micro USB). However, the dock doesn't appear to have a USB pass-through, so, it acts EXCLUSIVELY as a charging station! So... why the USB plug and if all it's going to do is charge, I may as well just keep plugging it in! Am I overlooking something?