That’s a great explanation. I wonder if anyone has looked at using materials other than air between the parts?
A motor could be filled with oil, but the problem of preventing oil leaks through the bearings would be insurmountable.
Keeping vacuum inside the motor would be even harder. Enclosing completely the motor in a case and using a magnetic coupling through the wall might be a solution to avoid holes in the case, but it would greatly increase the cost and it would be complex to ensure lubrication for the through-the-wall coupling.
No such solution seems acceptable, so besides microscopic motors the only other possible application for motors with electric forces would be in some motors intended to be used in satellites, on the Moon, or in other such places where the motors could operate in vacuum.
Shouldn't be too hard for stationary applications if you stick to a vertical axis and allow gravity to help keeping oil and air separate. I guess neighbor post's viscosity counterargument will do fine in its own though.