Thats not necessarily only deinterlacing - lots of modern codecs are doing compression (pretty much all of them) based on how much change there is frame to fram

Thats not necessarily only deinterlacing - lots of modern codecs are doing compression (pretty much all of them) based on how much change there is frame to frame. But almost nothing is interlaced these days. Although of course interlacing itself was a simple form of what you are describing above in a way.