They don't need it as long as
a) the VR market is still a niche, and those who would be willing to spend even more to get two expensive high-end graphics cards are an even tinier niche
b) they can sell off their entire production capacity easily to gamers & miners.
We will probably have to wait for another couple of years until VR catches fire on the main stream market, and you see dedicated twin-GPU graphics cards for VR appear, supported by a truly functional driver implementation (and without any micro-stuttering/timing issues which so far has been an issue for SLI).
@neal_white_iii: I am exactly in the same spot as you are - owning the 980Ti, waiting for the 1180Ti. Seems to make most sense to me in terms of easy-to-use GPU power for money, where I do wish to get a lot of GPU power nevertheless. As my 8K may only arrive towards the end of the year, and the ETA of my 8K(X) is completely unpredictable at this stage, waiting for the 1180Ti will not mean such a long wait after all...
[Edit: given the newest update from Pimax, who knows, perhaps I will receive my 8K in August after all... I will likely still remain patient because there is little point in upgrading to the 1080Ti to sell it 3-6 months later, but it would hurt a bit...]