Here is the way it has been historically. American dishwashers were originally made with one
motor/pump assembly which both washed and drained the unit. This was true all the way past 1990 on most brands. They contained a reversing motor.
Only GE made a one-piece assembly and still does, but the motor does not reverse on these.. (wd26x10013
Most all of the new models made after 1998 by other manufacturers now have a separate electric drain pump which is not part of the wash motor. Non-reversing motors are cheaper to make, hence the change. The drain pumps on new models are quite small and just strong enough to pump water out while saving a lot of energy in the process versus using the main motor.