Let's consider the Bent Pyramid at Dashur.
In the image above one can see the causeway heading in a NE direction between the perimeter wall to the Valley Temple (the Mortuary Temple having been removed). At this temple, the causeway then detours in an easterly direction to what is speculatively called a "basin" or "harbor" as seen in the plan below.
If the causeway was a utilitarian project designed for easier transportation of materials, why the detour? Why not just a straight line, and why through a temple?
Compounding the question mark over the reason for the causeway is the fact that it is very narrow; is surrounded by high mudbrick walls and was covered with a vaulted roof, as seen below.
Added to this, is the discovery that the causeway had a pedestrian underpass. Obviously, the pedestrians were not too concerned about the heavy loads above.
For those who may wish to explore an alternative reason for the construction of causeways, I recommend perusing the paper by Amelia Carolina Sparavigna who postulates that this causeway has connections with the position of the moon and has an astronomical/mystical purpose.