They are made, ready to ship in some Hasbro manufacturer's wherehouse, but Target, Walmart, and Toys R Us don't want to buy them because their computer inventories are not running up sales of
and there is not room for more 12" figures that don't sell.
There is no human component to the equation either, so don't hide the Zam Wessels. If the computer doesn't show sales, it won't order.
So where's Lando Skiff? Unwanted by the majority of the population according to a computer.