It has to do with the shaped granite and the much heavier megalithic stones.How do we know the Egyptians didn't use the wheel, simple pulleys or cranes or other things of that nature? Are we relying on their writings and pictures that are recorded?
The whole "we don't know how the pyramids were built" thing seems kinda Alex-Jonesy to me, I always just assumed they had clever manual techniques that we've forgotten simply because we didn't need them or invented better techniques.
King Tut's tomb and all of the tombs in the Valley of Kings were carved into limestone bedrock. Using simple copper chisels and dolomite pounding stones a single worker could remove almost a square meter a day of limestone. This has been tested in the modern era and copper chisels and such have been found in great number in the region. Giving material evidence of the tooling they used to create things like royal tombs.
With the tools we know they had, and wheels and such existing clearly in the historical record later the general consensus is that they did not have them at 2600BC when it is accepted that Khufu had the Pyramid built. We also know that they had a culture of building boats out of reeds and whatnot.
So how were all these massive granite stones moved and shaped? That if we look at modern attempts on even a small scale would have taken years upon years for just one of them. And there's thousands of these things.