Mac binaries don’t support CUDA, while the CUDA and cuDNN libs are shipped with the Linux binaries, which makes them quite large.
I’m not using Windows personally, but based on the install instructions on the website 1, it seems you can install PyTorch on Windows using pip, e.g.:
pip3 install http://download.pytorch.org/whl/cu80/torch-0.4.1-cp36-cp36m-win_amd64.whl