Many of the specialized servos and motors, as in the case of machine tools are specially built for that application.
Many of the motors have alternative resolver types or specially set feedback angles, and the servo drives have dedicated, often digital interfaces.
Again, these items once repaired can be run, and proved to work before returning to the customer. Many of the robotic hand-held pendants are also repairable, often these items are at the receiving end of harsh treatment from operators and a cost effective repair is a bonus.
Makes such as Kuka, ABB, Fanuc and many more.