In business and in life, it's the squeaky wheel that gets the oil. On the assembly line, it's also the bearings, gearboxes, cams, linear actuators and anything else that moves side to side, up and down, or around an axis.
Without lubrication, even the fastest, most accurate, most elegantly designed assembly system will literally grind to a halt. Lubrication does more than just reduce friction between moving parts. It also prevents corrosion, dissipates heat, and keeps mechanisms free of contamination.