And that brings me to the question of why Apple needs a connector that supports more than USB? USB2 is good enough to stream audio and video, as well as data and power. I bet they won't support USB3 either once it starts migrating down to other mobile devices.
Indeed, apparently USB-to-Lightning cables are all USB2. Then again, it may be possible to upgrade it to USB3 later with a firmware revision.
As for not using USB2, the only thing I can speculate is whether or not it can handle HD streaming. One thing that Lightning is meant to do is do HDMI output.
Actually, that raises a question for me. As someone who's not terribly au-fait with Android, are there equivalent devices and connectors that allow you to plug an Android device into your stereo/HDTV/whatever? I assume there must be...
I have a £5 connector that plugs into the micro USB port on my HTC One X and runs into an HDMI plug on the TV. It can mirror my screen and also stream movies off the phone. Needs to be powered but that can also be from a USB on the TV. A cool but not often used feature for me, but I suppose I could do powerpoints for work that way.