Another way to use stepper motors is to put encoders on the stepper.
Then accumulated error is less and correction steps can be made.
That's basically what a closed loop MaxNC mill or router does on the axis drives:
MaxNC
If the goal is low RPM discrete movements over partial rotations steppers have a very valid use case.
If the goal is higher RPM discrete movements over higher numbers of rotations motors rigged to be servos make more sense.
In CNC case it is common that servo drives like those from Panasonic on my larger home brew tools are AC motors with encoders and for short low speed movements I need to use gearing or cog belts to get the speed down and the keep in the higher torque operational area of the servo. For occasional short movements it's okay to not gear down but honestly it is hard to just use the servo output shaft in most cases. Really same problem with FIRST drive trains and CIM motors. Stepper motors start to have decreased torque output the higher the output RPM where as servos tend to have higher torque in an RPM band higher up.
If my CNC work area is small, like say a 3D printer, it makes no sense to implement a full servo just so I can gear it down or do something with the electronics to push power into the motor and maybe blow past my intended target position. It makes more sense to use a stepper motor that tends to move slowly in discrete steps at higher power and catch the errors - with the extra bonus if a missed step is caught by the stepper with encoder it can be tried again which often works great with cutting tools pushing through materials.
Just to put it in perspective: servos with reductions can run at higher RPM with higher power than steppers so where professional larger size CNC is concerned (run time is directly proportional to production volume and money) I'd want the more expensive servos.
Course there's the short movement intermediate case of hobby servos. In the hobby servo case the target position and the desired kind of movement is more to be smooth and close enough. Also it was likely cheaper to make the plastic gear boxes in volume than create the electronics when those first appeared on the market.
Radio Control History