why all the Primitive unit cells do not show the other possible variations like Body Centered, Face centered etc..?

As we know unit cell is building block of crystal lattice. There are two distinct types of unit cell: primitive and non-primitive. Primitive unit cells contain lattice point only at the corner of unit cell. Non-primitive unit cells contain additional lattice points, either on a face of the unit cell or within the unit cell. The classification of unit cell is shown below:

Since in primitive unit cell lattices are present at the corners of the lattice only we cannot draw the different variation of it. It can change the geometry from simple cubic to tetragonal or other else as shown in diagram below: