GPU workloads always want some odd driver that has a gigantic download, and they're constantly coming up with new reasons to force you to the newest APIs, which means you have to buy new chips that have the right architecture or firmware for the new APIs.
So I have to buy this co-processor, and then I can't even treat it like a black box that I send commands to, I need a gigabyte-scale SDK or something to issue the commands on my behalf.
I can't stand it. It's as if there was a tiny window when programming was simple, after I learned about FOSS, and before GPGPU caught on. As if the personal computer really will turn out to have been a fad.
Despite the trade offs those systems made, consumer GPUs ended up with better performance because a lot of the things and general CPU has to do interfere with performance of pure numerical computation.