[posix_me_less]

If one turns off special effects (compositing) and uses low resolution, even the cheapest mainstream gpu is sufficient to draw 2D text, lines and icons with 60Hz framerate. However, people expect to get more in graphics output than 10-20 years ago, so they buy high-res displays or turn on additional graphics effects in graphics environment - and then, we do need powerful GPUs, because those resolutions and effects require high computing power that is best to provide in a powerful GPU, not powerful CPU.