Gravity is an observable phenomena that can be evaluated and tested.

Using a spell to allow a soul to pass from one life to another cannot be evaluated and tested. And, more importantly, it isn't evaluated or tested. There is no effort to determine whether said spell worked or did not work. It is a function of belief, therefore, the spells are invoked the ceremonies are performed and everyone goes home after it is over.

On the other hand, gravity and applications of gravity are very will evaluated and tested. You cannot fly planes, rockets or shoot cannons accurately without continually applying, validating and testing your data using gravitational computations.

Spells, magic and ritual are a function of belief. Math and architecture are a function of empirical observation and provable facts. I don't think that the Egyptians thought of work as being "magic". They thought of it as we do and everyone else does, work. Therefore, building a pyramid was not "magic" it was work. The number of laborers were calculated, the amount of houses they needed were laid out, the amount of food they would require was calculated and the dimensions of the stones were calculated, cut and refined, the ramps were built, the reliefs were carved and everything else done as a reflection of human intellect. The pyramids were not built with magic and I don't think that the Egyptians looked at it as anything else but a monumental labor project, that kept the minds of the mathematicians and architects sharp and the workers busy, not magic. And given the level of organization and sophistication of the Egyptian state, I am sure that they recognized the value of organization and planning as part as the success of their culture as much as they did the belief in magic and ritual.