The 8GB version is selling at zero profit margin or on loss till people purchase stuff of Play store and tie their future with Android tablets. If there were SD Card why would any customer consider the 16GB version that actually has a tiny yet tangible profit margin? (Margin during sale of the tablet as opposed to profit from content on Play store later).
In fact we aren't even expected to buy the 8GB version.
The only major negative is the 8GB version being 8GB! With no SD Card
support google has gone the route of Apple to make up for the lost
profit in 8GB version from the 16GB customers.
Of the 8GB, JB eats up 2GB and only 6GB are available for your
downloads. One HD movie, few songs and books will fill it in no time. So customers better go for at least the 16GB version till USB/... mounting of some external media is hacked in.
The 8GB version is selling with hardly any margin.
The 8GB version is just to entice you to consider Nx7 line before you ultimately end up choosing the 16GB version.
It should be obvious that the 16GB has just $5 worth of extra hardware while costing $50 more.
ps: other minor gripes include adobe backing off flash support and no
camera on the back (which we better not use on any tablet to be
acceptable in the society;-)).