Why can't I use GPU rendering in Blender? Why is it that Blender will only allow me to render with a CPU (GPU choice is unavailable)? Or is it until I acquire a graphics card that is specially built for such a task?

The images below show a Dell System Diagnostics (Video calibration) and GPU-Z results.





Platform: Dell Inspiron 3521 notebook with Core&nbsp;i3 Intel HD Graphics 4000
Blender Cycles relies on GPU compute languages like CUDA or more recently OpenCL. CUDA is exclusive to Nvidia and while OpenCL is technically cross platform, in practice AMD's implementation is the only one that provides a usable speedup for Cycles. 

From the Blender wiki:

https://wiki.blender.org/index.php/OpenCL

... Intel GPU’s are getting more powerful but are not a good target yet and CPU based opencl provides little or no benefit over CPU based cycles.