A Point Charge?

[abrowaqas]

Why do we take a point charge always while estimating the electric field intensity of a system of charge? as in Coulomb's and Gauss's Law etc.

[graphene]

That is how electric field is defined.
The electric field of a system of charges at some point is the force that would be exerted on a unit positive (point) charge at that point.

[Ali Inam]

As we can have many different types of surfaces, therefore we consider a point charge in our most examples. Because, this is what we say in Electric field, we consider one part of it while defining it