I think that if you are a game dev and you want to sell your game to as many people as you can, then adding things like FSR and DLSS should be a no brainer, especially since both are now very easy to integrate. These things will increase your target audience by a lot, especially FSR. If you are not doing it, it's either because you are lazy ( or stupid ) or you have an exclusive contract with AMD or Nvidia to promote their features, like probably Godfall has or some of the games sponsored by Nvidia.My point is it isn't like devs needed to wait for FSR to start doing that. While a bit more work to achieve fall back results like FSR if a dev was inclined to go to that effort they could have done so already.
It doesn't even matter if you worked on your own upscaler, if you want to make money you give them as much options as you can. Are they happy playing with DLSS or FSR? Give them whatever they want.