It was epic in the past seeing Intel Pentium laptops with dedicated GPU. You could upgrade it and maintain the decent GPU.Probably because it doesn't. You see Stoney / Bristol Ridge with a low end discrete AMD GPU (example), which suggests that AMD charges a premium for its higher end chips.
It may also be that it's easier for OEM's to use discrete GPU's because they have consistent performance regardless of the CPU memory configuration.
Still having an Acer with ATI Radeon GPU with an upgraded Core i3 380M from a Pentium P6000.
And I was hoping to see it again... even an Atom with a low tier dGPU to maintain the CPU being used to their limits.