Why does Intel still add such a large iGPU to their processors? It seems that for such a high end desktop, like a i7 quad core skylake, it's unnecessary to do so since no one will be running those without a dgpu anyway. Visually, we can see that an equivalent amount of space of 4 cores is used by the igpu; surely at this point it makes more sense to scrap the igpu on higher end models and replace it with four extra cores?
Intel does this actually. The i7-6800k has 6 cores with no iGPU and costs about 400 dollars which is only a little more than the i7-6700k Skylake which is about 340 dollars. If you increase the cores further it can get quite expensive though, the 10 core i7-5960x with no iGPU is about 1600 dollars. iGPU's are popular because many consumers don't need a dedicated GPU/more cores (say if you were just browsing the internet, doing word processing, etc.), especially in laptops where it might present a power issue.