My guess would be that in previous generations people were not exposed to as much abstract information, nor were they expected to remember it, and if they were

My guess would be that in previous generations people were not exposed to as much abstract information, nor were they expected to remember it, and if they were expected to remember something there was a social structure or a regular habit which helped. Individuals are responsible for a greater variety of tasks than they used to be, and those tasks are much more abstract, and so it also becomes more difficult to form memories about the details.