Titangeek wrote:
This is a question that has been bugging me off and on for a while, so, why did they?
I think your question is a bit like asking why did cave men only paint in caves. Well, they probably didn't. It is just that anything painted outside wouldn't have survived into the modern era, so we don't get to see it.
The Egyptians had documents in papyrus, but these obviously decayed or were burnt or just thrown out over time, so the oldest of them extant is around 2000 BCE (if Will Durant is to be believed), while inscriptions on stone go back to at least 5000 BCE. But this does not mean there weren't papyrus documents coincident with these oldest stone carvings, just that they weren't written on as durable a material.
A weird counterpoint to the above is Babylon, and perhaps Sumeria. Given the building materials available to them, they built their cities out of porous, water absorbent brick, and did their writing on clay tablets which were later baked. The architecture returned to the mud they made it from, but the clay tablets were virtually indestructible, at least via weathering or bugs or even immersion in water. So, there's extant writing on clay tablets from Babylon, but not much architecture. And lots of architecture in Egypt, but a lot of long-gone papyrus. For all we know the Babylonians wrote on their walls and pillars every bit as much as the Egyptians did. Or not.
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"The man who has fed the chicken every day throughout its life at last wrings its neck instead, showing that more refined views as to the uniformity of nature would have been useful to the chicken." ? Bertrand Russell