I recently read in a book that static friction is zero for a rolling body, and this explains why it doesn't slow down the rolling body. However, if static friction is zero, how does the body grip the floor to prevent it from slipping?

In the book I read, in the free body diagram of a rolling body moving with uniform velocity, static friction was not included. But in the free body diagram of a rolling body upon which a horizontal force has been applied, the force of static friction has been included and friction has also been included in the equations of motion of the rolling body.

Why has friction been included only when an external force is applied?

I recently read in a book that static friction is zero for a rolling body, and this explains why it doesn't slow down the rolling body. However, if static friction is zero, how does the body grip the floor to prevent it from slipping?

In the book I read, in the free body diagram of a rolling body moving with uniform velocity, static friction was not included. But in the free body diagram of a rolling body upon which a horizontal force has been applied, the force of static friction has been included and friction has also been included in the equations of motion of the rolling body.

Why has friction been included only when an external force is applied?

And is static friction really zero for a rolling body?