Because that's been a thing for years already - and works way better then this research does.
Unreal engine 5 has been demoing these features for a while now, I heard about it early 2020 iirc, but the techniques like gaussian splattering predate it.
I have no experience in either of these, but I believe MegaScans and RealityCapture are two examples doing this. And the last nanite demo touched on it, too.