Although it is possible to have position feedback in stepper systems, most don't, and therefore are at the mercy of the motor/driver combination to not miss any steps. Also, no warning is given if steps ARE missed, without position feedback.
Some of the other drawbacks of steppers are substantial uncertainty of the actual position of each 'step', resonances at certain speeds, great loss of torque at higher speeds, and waste of power leading to substantial heating while standing still.
The advantages are that stepper motors are somewhat cheaper than servo motors, and the lack or the feedback components further reduces costs.