GPU drivers are notorious for being out of tree and even there most GPU drivers over the years have been upstream. Even if you limit to just GPUs AMD are not the same as Nvidia. The in-kernel AMD driver is the primary one these days and even Nvidia has finally relented and is finally helping move at least the kernel driver upstream. That Nvidia's closed-source driver has been a mess for all these years is just a further example of how the Linux model is much superior to the Windows one.
