That's a good observation. I think of cables as an anti-feature. ( as defined by Benjamin Mako-Hill ).

In that, the devices are perfectly capable of syncing and tethering wirelessly, but Apple hasn't enabled that functionality yet. They are going to add that at some point for an extra 9.99$ and going to call it AirTether. Brand new feature of iPad3. You pay a premium for getting rid of cables.