NV were butthurt about consoles so put out gameworks (ironic name really) to counteract any potential benefit AMD might get from developers working with GCN on all platforms.
Nvidia's gimping with gaming is doing wonders for Nvidia cards, successfully gimping a 290X to the point that it performs around GTX 770 on Project Cars. Worrying that even if the 390X is say 20% faster in performance than Titan X, gimping with gameworks could potentially make it perform worse in gameworks titles..
This is a brutal industry