Why is magnetic locking or cogging not present in a DC motor?

Why does magnetic locking happens? Well it happens in induction motor mainly due to its working principle. The stator coils in the motor is supplied by single/three phase AC supply. As a result of this supply, the stator coils develop their own respective magnetic polarity. Now, as the supply is time-varying, there is time-varying magnetic field also which induces emf in rotor conductors.

Brushed DC motors don’t have cogging because of their contruction and principle of operation.
Brushless DC motors have cogging torque.

Because there is not salient pole infrastructure for the cylindrical rotor of the DC motor armature mounted on the rotor.