The main reason an engineer might decide to design a circular foundation for an structure

is:

It might match better with the shape of the structure $($e$.$g$.$ a water tank$)$

Cost saving, as circular foundations are generally cheaper to build

To minimize the thickness of the foundation

To minimize the differential settlement

To get higher bearing capacity

Circular foundations are easier to construct

Because it is easier to place the column load right at the center of the circular foundation than other

foundations

To minimize overall settlement