Why not using GPUs as a CPU?

Question

I know the question is only partially programming-related because the answer I would like to get is originally from these two questions:

Why are CPU cores number so low

Answer 1

GPUs are designed for graphics related processing (obviously), which is inherently something that benefits from parallel processing (doing multiple tasks/calculations at once). This means that unlike modern CPUs, which as you probably know usually have 2-8 cores, GPUs have hundreds of cores. This means that they are uniquely suited to processing things like ray tracing or anything else that you might encounter in a 3D game or other graphics intensive activity.

CPUs on the other hand have a relatively limited number of cores because the tasks that a CPU faces usually do not benefit from parallel processing nearly as much as rendering a 3D scene would. In fact, having too many cores in a CPU could actually degrade the performance of a machine, because of the nature of the tasks a CPU usually does and the fact that a lot of programs would not be written to take advantage of the multitude of cores. This means that for internet browsing or most other desktop tasks, a CPU with a few powerful cores would be better suited for the job than a GPU with many, many smaller cores.

Another thing to note is that more cores usually means more power needed. This means that a 256-core phone or laptop would be pretty impractical from a power and heat standpoint, not to mention the manufacturing challenges and costs.