Why are stepper motors used for precise positioning?

Stepper motors are open-loop, cheap, easy to use, and durable motors. They offer several advantages over other electric motors: they have high torque at low speeds and standstill; their speed is easy to control via input pulses; their marginal positioning error is non-cumulative; they have an excellent response to start/stop. This makes stepper motors the obvious choice when precise and reliable positioning is needed.