The Pyramids have lasted quite a long time. Resting the outer casing would help to make it last quite a while longer and show us how the pyramid looked at the beginning. Thats my unqualified 2 cents.
The nice casing stones on the Great Pyramid and those missing on Khafre (the second biggest at Giza) were stripped by the muzzies. In recent centuries they dismantled the remains of the unfinished Djedjefre pyramid at Abu Roash.