This paper reviews the possibility of using single-motor drives to build lightweight robotic systems such as walking assistive exoskeletons, aerial robot manipulators, and collaborative robotic manufacturing systems. A single-motor drive realizes multi-axis motion actuation with one central motor, a mechanical power distribution system, and clutches at each joint. In a product family of motors that share the same design features, the models with higher powers are usually not that much heavier than the ones with lower powers. This fact motivates the replacement of conventional one-motor-per-DOF systems with single-motor-drives, so that the overall power-to-weight ratio of the system can be increased and the weight can be reduced. Related discussions, though have been published before, are very few. This paper examines the limitations of the existing work and propose alternative designs to improve. The corresponding control strategies are also presented. A simulation study is provided to demonstrate the proposed designs.