The fact of the matter is that a lot of people have no use for an accelerated graphics chip. Think of all the people that only use their PC to surf and write emails. Then consider that these numbers also reflect machines in offices. These buyers specifically don't want good graphics hardware because they don't want people playing games at work.
At my office my immediate group is running about 12 machines, and we have no use for a graphics accelerators on these machines. I have a nVidia GeForce 2 GTS in mine which serves up nice 3D screen savers, but that's about it. Most of the group have whatever graphics card came with their box, either a low end ATi or nVidia card or integrated Intel graphics. I only have the GeForce because the TNT2 it came with died a while back, so the techs slid me a GeForce they had laying around - it works fine for a 1600 x 1200 2D desktop.