"On an unrelated note, I wonder why they were wasting all these massive logistics into piling rocks in middle of the dessert, when they could, you know, be building roads or dams or walls across all their frontiers"
Was that rhetorical?
In case not: religion. They believed it served a higher purpose. The afterlife of their godlike emperor. And all who took part and did good, got better chances of a better afterlife themself ...
I honestly believe religion to be mostly an instrument to convince people to follow a certain agenda. Which means, from my point of view, that there must be a real reason for the Egyptian religion to promote the construction of pyramids instead of more, let's say, practical goals.
This is definitely what religion was and is widely used for, but I am very sure, that the Pharaoh's for example really believed, that they were incarnations of a god.
I mean, imagine you are being raised up this way, everyone bows his head to you as long as you can remember and they do believe that you are a god in human form ... how can you not believe likewise?
Besides, I met quite a lot people by now who were not raised like this, but developed such an ego that they consider themselve to be enlightened and allmost godlike ...
Also, building a big monument for your glory, is a very practical goal, even if you do get doubts, about there usefulness in afterlife, but when everyone of your underlings measures your greatness in the size of your grave, than you also really have not much choice ...
Was that rhetorical?
In case not: religion. They believed it served a higher purpose. The afterlife of their godlike emperor. And all who took part and did good, got better chances of a better afterlife themself ...