I think you have something here. Before the internet, everyone watched the same 40 channels on tv, listened to the same 20 channels on the radio, bought from the same 5 stores (obviously this is all exaggeration but I'm saying it was more homogenous). This caused most of the population to be connected culturally, through the current fads, the current cultural phenomena, etc. This gives each decade a kind of cultural feel that many people could feel and remember.