I can't find many authoritative sources, but it stands to reason that in a mostly agrarian society, there'd be fewer people who could write, would have access t

I can't find many authoritative sources, but it stands to reason that in a mostly agrarian society, there'd be fewer people who could write, would have access to good writing materials, specifically materials with longevity, and get those materials into hermetically sealed environments that would ensure their integrity for a couple of millennia.