Answer: allow a range of motions in the driveshaft
Explanation: it is also known as universal joints and working angle refers to angle between two shafts that the joint connect. when the working angle exceeds certain threshold, it can cause vibration in which it can turn into failure thus limiting the angle is important. so the mimimum working angle is 1/2 degree.
limiting the angle to 1/2 and angle beetween the shift is possible and thus reducing the risk.