Lots of the Intel cards are low bar OEM, have little video memory and only really support fixed function pipelines rather than shader models. So you can't make

Lots of the Intel cards are low bar OEM, have little video memory and only really support fixed function pipelines rather than shader models. So you can't make stuff look as good and the bottom end of the market dictates how much stuff you can do 'mainstream'. Meaning lots of cards can't handle shaders which improve rendering quality immensely and put it on the GPU.