Anonymous sources told the site that AMD needed more time to finalize the hardware and the software, and that the firm didn't want to put extra pressure on the Christmas sales of its Radeon Fury and Fury X models.
After an initial shortage at launch, it took AMD a few months to ramp up the production and they felt rather good about the quantities that went into channel. Releasing a dual chip card would pressure on the Fury X sales and mean a possible price drop. AMD didn’t want to do that as it needs to make as much money as it possibly can in 2015 GPU sales.
The second reason was software and hardware related. It is hard to make the good driver that can take an advantage of this card. The dual chip cards are always tough to make. Sometimes the software scales well and sometimes it throws its hands up in dispare on selected titles.