I’ve said the same. They aren’t mentioned by the Greeks either, even though they had established cities in the Nile delta (like Alexandria) and could visit them very easily. The only real reference is in Herodotus’ Histories, but even then they are described wrong and are spoken of more mythically, just like when he speaks of giants living to the north, etc. The pyramids are also not mentioned or depicted through the Renaissance.

I believe that when Napoleon spent 3 years in the deserts of Egypt, that’s when they were built. The real ancient ones were the smaller step pyramids which we now call the proto-pyramid designs. After Napoleon, the age of Romanticism began, when there was suddenly a massive uptick in the number of paintings depicting the pyramids and the sphinx. And the treasure hunter phase started, with people trying to get into them.