>Is there a reason codec's don't use the previous frame(s) as stored textures, and remap them on the screen? I can move a camera through room and a lot of the texture is just reprojectivetransformed.

I mean, that's more or less how it works already. But you still need a unit of granularity for the remapping. So the frame will store eg this block moves by this shift, this block by that shift etc.