Upscaling is useful if for whatever reason you need a target framerate that your GPU can't sustain at your desired resolution. I.e. roughly, you reduce target resolution which allows GPU to render more frames in the same time period, then you upscale the result to counteract that resolution reduction. That way you trade image quality for higher framerate.
In the network case (i.e. "streaming"), you are limited by the bandwidth and latency of the network itself. I.e. you will sooner bottleneck by the network than by GPU being unable to render frames faster than that. So upscaling is just pointless for it.
I don't think that's true though. It's not very bandwidth demanding to stream 4k 60fps or 1440p 120fps, GeForce Now does that already out of the box for less than 100 Mbps.
But it's hard to sustain those frame rates at max graphics. Ue5 will raise the ceiling quite a bit too. The gfx cards will continue to be a bottleneck for AAA games.
Upscaling is more useful if you need some crazy framerates (like 240 fps) with high graphics settings for some reason. Even most high end GPUs can't handle that for demanding games on common resolutions. Or more reasonably for mid range and lower end GPUs which are just weaker and can't handle even 144 fps for the above without upscaling.
But low end GPUs use case isn't relevant for streaming since they can have highest end ones. So we are talking about those who want to push those crazy framerates, and I don't think networks allow that even if GPUs can sustain them.
Some middle case can happen I suppose if you get an outlier super demanding game, but I always saw it as questionable to push max settings if you are ready to trade image quality for more framerate with upscaling anyway. I'd rather stick to lower framerate and keep image quality of max settings intact by avoiding upscaling. So I just don't see a value in having it, let alone in dedicated hardware vs something like FSR which can work on regular compute units.
In the network case (i.e. "streaming"), you are limited by the bandwidth and latency of the network itself. I.e. you will sooner bottleneck by the network than by GPU being unable to render frames faster than that. So upscaling is just pointless for it.