If the pyramids were made of something like concrete why go to the trouble of casting separate stones then dragging them into position?

Some stones have been liad with their bedding plane vertical - shoddy workmanship.

The idea of cast stone in building the pyramids is simply someone's Bright Idea.
It is quite obvious that the blocks are natural stone--you can see the fossils of shells and other sea creatures in them, showing that they are sandstone. (originally the bottom of a sea)
Referring to shoddy workmanship. If it IS so shoddy, how could they last for four thousand years and counting? I can't think of any other workmanship that has lasted so long.