Years ago, when hockey gloves were stiff and harder to open and close, the knob at the end of the stick was much larger. When a player dropped a stick on the ice, the larger knob raised the stick off the ice enough that a player could still be able to pick it up easily and efficiently.
Gloves today are much different, and the large knob is no longer necessary. In fact, a knob that is too big actually can create bad habits that can be difficult to break, such as rolling the stick into the palm of the hand, as opposed to holding it with your fingers.