Question

Natural numbers are a subset of Whole numbers so why are Natural numbers required?

Answer 1

That is because they are easier to study and some of their properties may be useful for whole numbers which simplifies the learning process.

In the same way you will ask that why whole numbers are required as they are subset of integers.
or
why integers are required as they are subset of rational numbers
or
why rational numbers are required as they are subset of complex numbers.


All these we need to study as they make the learning and teaching process easier.