Nvidia is the only real option for AI work. Before Trump lifted the really restrictive ban on GPUs to china they had to smuggle in GPUs from the US, and if you're Joe Schmo the only GPUs you can really buy are gaming ones. That's why the 5090 has been selling so well despite it being 2k and not all that much better than the 4090 in gaming.
Also AMD has no high end GPUs, and Intel barely has a mid range GPU.