Stepper motor VS Servo motor

Why is it said that the stepper motor is an open loop, and the servo motor is a closed loop

If the stepping motor adopts the servo-corresponding control method, it has most of the characteristics of the servo, but the cost is only 1/2 of the servo, and the servo does not have the problem of zero-vibration.

Servo motor has more encoders than stepper motor, so it has more feedback function, so it forms a closed loop.
The stepper motor without this encoder is open loop.

Related link : Setpper Motor | Servo motor