Huh. So, honestly: I think that was actually a horrible decision. I just found the box, and the only thing related to this in the manual is the fairly overly-typical "use only the USB charging unit that comes with your Nexus 7; using a different power adapter may damage your tablet" warning. It says nothing about the cable.

I, like many people I know, end up having multiple cables: even non-technical people I know often end up buying an extra cable, so they aren't screwed if they lose one. A lot of people who splurge for Android tablets probably also like Android enough to have an Android phone, so they will simply already have a micro-USB cable lying around anyway.

Assuming this is true for a second (and I currently have no reason to disbelieve you), I have a friend who was actually complaining just a few days ago that "my nexus 7 is really, really bad at charging". We were all discussing it, many of us commiserating that the Nexus 7 seems to be the worst of all of our devices when it comes to charging.

However, now, it could be that we are all just using "the wrong cable", because no one at Google thought it important to mention "this cable is a magic voodoo cable; the manual might claim it is micro-USB, but you cannot use a normal micro-USB cable to replace it". At least with Apple, I can look at the cable and tell if it will work for me or not.