If you were doing work on why empires collapse with almost total certainty, like the Roman, Greek, Egyptian, Spanish, British, Chinese etc etc, then you'd only need to look at a thread like this to see why.
The Pyramids were for burial, it's clear to anyone who has been inside one, and clear to anyone with half a brain and uses it, that this is the case.
The inside of a pyramid. If you were going to store grain, you wouldn't store grain like this. Total lunacy.
The largest pyramids echo the skies too. There are various theories,
Orion correlation theory - Wikipedia, the free encyclopedia the Orion correlation theory suggests that the three main pyramids were Orion's belt, potentially the Nile was the Milky Way.
Why do all of that for grain?
Well, a little bit of research and you'd realise it has nothing to do with grain. Did they find lots of grain inside? No.... so....?