Probably cause people got distracted by TV, Music and Video Games :)
Also during the cold war years I think most people were too stressed out to produce much. I do like to think that in the 80's extremes like oversaturation (think all the cartoon series of that time) were pretty prevalent.

I wonder what would happen if you'd do something similar with music (maybe album covers?). Perhaps if you have a sound wave along with the visual data maybe we can "fill the hole" during the 80s.

Awesome post btw.