Graphics Processing Units, or GPUs as they are more typically shortened to, are typically marketed to and focused on the hardcore gaming market. It's typically gaming enthusiasts that expect an incredibly high-level of performance from these graphics cards in order to ensure that they have the smoothest possible experience while playing computationally expensive 3D video games.
Video games require millions upon millions of calculations per minute to be done in order for the computer to know exactly where to render 3D objects in a game. A typical scene within a game could contain anywhere from a handful of simple 3D objects to thousands of incredibly complex models. So, with each frame, we need to decide their exact relative positions, scales, rotations, and a whole multitude of other factors in order for them to be successfully rendered.
Even models that we deem to be relatively simple could be made up of hundreds or even thousands of different vertices. Look at the following...