What is the purpose of drawing a social pyramid?

A social pyramid is aimed to defined a social structure, where powerful people, like presidents, are in the top. And common people is in the bottom.

Also, a social pyramid is used to specify the importance of each social step. For example, in a democratic government we can that the base of the pyramid if the people, they are the most important part of the government, without that base, the pyramid falls.

In the social pyramid of ancient Egypt the pharaoh and those associated with divinity were at the top, and servants and slaves made up the bottom