Sorry, what I meant was, what if the GPU and the motherboard fused into one unit. So the CPU and main memory in but the card is fixed.

I guess the main problem with that we have this cycle where most people have a single graphics card with one or two monitors plugged in, and the power users have two of them to drive four screens, or to have 2 cards drive one monitor by daisy chaining them together.

But in the case of the latter two, it's usually a problem of a bottleneck between the card and the main bus, which of course if you were making the motherboard, you'd have a lot more say in how that is constructed.